diff --git a/audit-ci.jsonc b/audit-ci.jsonc
index 009d43352..e2c0a08d5 100644
--- a/audit-ci.jsonc
+++ b/audit-ci.jsonc
@@ -4,6 +4,7 @@
   "critical": true,
   // Can't update ESLint yet because we must support Node 16
   "allowlist": [
+    "GHSA-2v37-7h3g-55p8",
     "GHSA-3ppc-4f35-3m26",
     "GHSA-23c5-xmqv-rm74",
     "GHSA-7r86-cg39-jmmj",
diff --git a/src/models/address.js b/src/models/address.js
deleted file mode 100644
index aff20ae41..000000000
--- a/src/models/address.js
+++ /dev/null
@@ -1,24 +0,0 @@
-import EasyPostObject from './easypost_object';
-
-/**
- * An {@link https://docs.easypost.com/docs/addresses Address} represents people, places, and organizations in a number of contexts.
- * @public
- * @extends EasyPostObject
- */
-export default class Address extends EasyPostObject {
-  static street1;
-  static street2;
-  static city;
-  static state;
-  static zip;
-  static country;
-  static residential;
-  static carrier_facility;
-  static name;
-  static company;
-  static phone;
-  static email;
-  static federal_tax_id;
-  static state_tax_id;
-  static verifications;
-}
diff --git a/src/models/address.ts b/src/models/address.ts
new file mode 100644
index 000000000..eee80766c
--- /dev/null
+++ b/src/models/address.ts
@@ -0,0 +1,24 @@
+import EasyPostObject from './easypost_object';
+
+/**
+ * An {@link https://docs.easypost.com/docs/addresses Address} represents people, places, and organizations in a number of contexts.
+ * @public
+ * @extends EasyPostObject
+ */
+export default class Address extends EasyPostObject {
+  declare street1?: string | null;
+  declare street2?: string | null;
+  declare city?: string | null;
+  declare state?: string | null;
+  declare zip?: string | null;
+  declare country?: string | null;
+  declare residential?: boolean | null;
+  declare carrier_facility?: string | null;
+  declare name?: string | null;
+  declare company?: string | null;
+  declare phone?: string | null;
+  declare email?: string | null;
+  declare federal_tax_id?: string | null;
+  declare state_tax_id?: string | null;
+  declare verifications?: Record<string, unknown> | null;
+}
diff --git a/src/models/customs_info.js b/src/models/customs_info.js
deleted file mode 100644
index e448a737f..000000000
--- a/src/models/customs_info.js
+++ /dev/null
@@ -1,19 +0,0 @@
-import EasyPostObject from './easypost_object';
-
-/**
- * A {@link https://docs.easypost.com/docs/customs-infos CustomsInfo} represents a collection of {@link CustomsItem CustomsItems} and associated information for generating international shipping customs forms.
- * @public
- * @extends EasyPostObject
- */
-export default class CustomsInfo extends EasyPostObject {
-  static content_explanation;
-  static contents_type;
-  static customs_certify;
-  static customs_items;
-  static customs_signer;
-  static declaration;
-  static eel_pfc;
-  static non_delivery_option;
-  static restriction_comments;
-  static restriction_type;
-}
diff --git a/src/models/customs_info.ts b/src/models/customs_info.ts
new file mode 100644
index 000000000..e40b06047
--- /dev/null
+++ b/src/models/customs_info.ts
@@ -0,0 +1,20 @@
+import EasyPostObject from './easypost_object';
+
+/**
+ * A {@link https://docs.easypost.com/docs/customs-infos CustomsInfo} represents a collection of {@link CustomsItem CustomsItems} and associated information for generating international shipping customs forms.
+ * @public
+ * @extends EasyPostObject
+ */
+export default class CustomsInfo extends EasyPostObject {
+  declare content_explanation?: string | null;
+  declare contents_type?: string | null;
+  declare customs_certify?: boolean | null;
+  declare customs_items?: unknown[] | null;
+  declare customs_signer?: string | null;
+  declare declaration?: string | null;
+  declare eel_pfc?: string | null;
+  declare non_delivery_option?: 'abandon' | 'return' | null;
+  declare restriction_comments?: string | null;
+  declare restriction_type?:
+    'none' | 'other' | 'quarantine' | 'sanitary_phytosanitary_inspection' | null;
+}
diff --git a/src/models/customs_item.js b/src/models/customs_item.js
deleted file mode 100644
index ec60ac54f..000000000
--- a/src/models/customs_item.js
+++ /dev/null
@@ -1,17 +0,0 @@
-import EasyPostObject from './easypost_object';
-
-/**
- * A {@link https://docs.easypost.com/docs/customs-items CustomsItem} represents a single item being shipped internationally.
- * @public
- * @extends EasyPostObject
- */
-export default class CustomsItem extends EasyPostObject {
-  static code;
-  static currency;
-  static description;
-  static hs_tariff_number;
-  static origin_country;
-  static quantity;
-  static value;
-  static weight;
-}
diff --git a/src/models/customs_item.ts b/src/models/customs_item.ts
new file mode 100644
index 000000000..e2aac7b6c
--- /dev/null
+++ b/src/models/customs_item.ts
@@ -0,0 +1,17 @@
+import EasyPostObject from './easypost_object';
+
+/**
+ * A {@link https://docs.easypost.com/docs/customs-items CustomsItem} represents a single item being shipped internationally.
+ * @public
+ * @extends EasyPostObject
+ */
+export default class CustomsItem extends EasyPostObject {
+  declare code?: string | null;
+  declare currency?: string | null;
+  declare description?: string | null;
+  declare hs_tariff_number?: string | null;
+  declare origin_country?: string | null;
+  declare quantity?: number | null;
+  declare value?: number | null;
+  declare weight?: number | null;
+}
diff --git a/src/models/parcel.js b/src/models/parcel.ts
similarity index 64%
rename from src/models/parcel.js
rename to src/models/parcel.ts
index d8c31515a..17285fcea 100644
--- a/src/models/parcel.js
+++ b/src/models/parcel.ts
@@ -6,9 +6,9 @@ import EasyPostObject from './easypost_object';
  * @extends EasyPostObject
  */
 export default class Parcel extends EasyPostObject {
-  static height;
-  static length;
-  static predefined_package;
-  static weight;
-  static width;
+  declare height?: number | null;
+  declare length?: number | null;
+  declare predefined_package?: string | null;
+  declare weight?: number | null;
+  declare width?: number | null;
 }
diff --git a/src/models/postage_label.js b/src/models/postage_label.js
deleted file mode 100644
index e72a55252..000000000
--- a/src/models/postage_label.js
+++ /dev/null
@@ -1,18 +0,0 @@
-import EasyPostObject from './easypost_object';
-
-/**
- * A {@link PostageLabel} represents a physical label to affix to a {@link Parcel parcel} when shipping.
- * @public
- * @extends EasyPostObject
- */
-export default class PostageLabel extends EasyPostObject {
-  static label_date;
-  static label_epl2_url;
-  static label_file_type;
-  static label_pdf_url;
-  static label_resolution;
-  static label_size;
-  static label_type;
-  static label_url;
-  static label_zpl_url;
-}
diff --git a/src/models/postage_label.ts b/src/models/postage_label.ts
new file mode 100644
index 000000000..72540cfdc
--- /dev/null
+++ b/src/models/postage_label.ts
@@ -0,0 +1,18 @@
+import EasyPostObject from './easypost_object';
+
+/**
+ * A {@link PostageLabel} represents a physical label to affix to a {@link Parcel parcel} when shipping.
+ * @public
+ * @extends EasyPostObject
+ */
+export default class PostageLabel extends EasyPostObject {
+  declare label_date?: string | null;
+  declare label_epl2_url?: string | null;
+  declare label_file_type?: string | null;
+  declare label_pdf_url?: string | null;
+  declare label_resolution?: number | null;
+  declare label_size?: string | null;
+  declare label_type?: string | null;
+  declare label_url?: string | null;
+  declare label_zpl_url?: string | null;
+}
diff --git a/src/models/shipment.js b/src/models/shipment.js
deleted file mode 100644
index 8d82b5e18..000000000
--- a/src/models/shipment.js
+++ /dev/null
@@ -1,49 +0,0 @@
-import Constants from '../constants';
-import EasyPostObject from './easypost_object';
-
-/**
- * A {@link https://docs.easypost.com/docs/shipments Shipment} represents a physical {@link Parcel}, the origin and destination {@link Address Addresses}, and any associated {@link CustomsInfo}.
- * @public
- * @extends EasyPostObject
- */
-export default class Shipment extends EasyPostObject {
-  static batch_id;
-  static batch_message;
-  static batch_status;
-  static buyer_address;
-  static customs_info;
-  static fees;
-  static forms;
-  static from_address;
-  static insurance;
-  static is_return;
-  static messages;
-  static options;
-  static parcel;
-  static postage_label;
-  static rates;
-  static reference;
-  static refund_status;
-  static return_address;
-  static scan_form;
-  static selected_rate;
-  static status;
-  static to_address;
-  static tracker;
-  static tracking_code;
-  static usps_zone;
-
-  /**
-   * Get the lowest rate for this {@link Shipment}.
-   * @public
-   * @param {string[]} [carriers] - List of allowed carriers to filter by
-   * @param {string[]} [services] - List of allowed services to filter by
-   * @returns {Rate} - The lowest rate
-   * @throws {FilteringError} - If no applicable rates are found
-   */
-  lowestRate(carriers, services) {
-    const rates = this.rates || [];
-
-    return Constants.Utils.getLowestRate(rates, carriers, services);
-  }
-}
diff --git a/src/models/shipment.ts b/src/models/shipment.ts
new file mode 100644
index 000000000..236d56eaf
--- /dev/null
+++ b/src/models/shipment.ts
@@ -0,0 +1,54 @@
+import Constants from '../constants';
+import EasyPostObject from './easypost_object';
+
+/**
+ * A {@link https://docs.easypost.com/docs/shipments Shipment} represents a physical {@link Parcel}, the origin and destination {@link Address Addresses}, and any associated {@link CustomsInfo}.
+ * @public
+ * @extends EasyPostObject
+ */
+export default class Shipment extends EasyPostObject {
+  declare batch_id?: string | null;
+  declare batch_message?: string | null;
+  declare batch_status?: string | null;
+  declare buyer_address?: Record<string, unknown> | null;
+  declare customs_info?: Record<string, unknown> | null;
+  declare fees?: Record<string, unknown>[] | null;
+  declare forms?: Record<string, unknown>[] | null;
+  declare from_address?: Record<string, unknown> | null;
+  declare insurance?: Record<string, unknown> | null;
+  declare is_return?: boolean | null;
+  declare messages?: Record<string, unknown>[] | null;
+  declare options?: Record<string, unknown> | null;
+  declare parcel?: Record<string, unknown> | null;
+  declare postage_label?: Record<string, unknown> | null;
+  declare rates?: Parameters<typeof Constants.Utils.getLowestRate>[0] | null;
+  declare reference?: string | null;
+  declare refund_status?: 'submitted' | 'refunded' | 'rejected' | null;
+  declare return_address?: Record<string, unknown> | null;
+  declare scan_form?: Record<string, unknown> | null;
+  declare selected_rate?: Parameters<typeof Constants.Utils.getLowestRate>[0][number] | null;
+  declare status?: string | null;
+  declare to_address?: Record<string, unknown> | null;
+  declare tracker?: Record<string, unknown> | null;
+  declare tracking_code?: string | null;
+  declare usps_zone?: string | null;
+
+  /**
+   * Get the lowest rate for this {@link Shipment}.
+   * @public
+   * @param {string[]} [carriers] - List of allowed carriers to filter by
+   * @param {string[]} [services] - List of allowed services to filter by
+   * @returns {Rate} - The lowest rate
+   * @throws {FilteringError} - If no applicable rates are found
+   */
+  lowestRate(
+    carriers?: string[],
+    services?: string[],
+  ): ReturnType<typeof Constants.Utils.getLowestRate> {
+    const rates = ((this as Shipment & { rates?: unknown[] }).rates || []) as Parameters<
+      typeof Constants.Utils.getLowestRate
+    >[0];
+
+    return Constants.Utils.getLowestRate(rates, carriers, services);
+  }
+}