Apple Inc. said its coming Apple Watch wearable would be available in a number of designs when it was announced in September. But the release of the Apple Watch developer kit this week added another important aspect about the watch, its screen resolution.

The Apple Watch will be available in two sizes -- one with a 38mm display and another with a 42mm -- but these models will also have distinct resolutions. The smaller Apple Watch will have a resolution of 272x340 pixels, while the larger Apple Watch will be 312x390, making both models high-resolution, retina display devices. The information was included in the WatchKit SDK, which Apple made available to developers Wednesday alongside its iOS 8.2 beta. Developers will now be able to create apps for the Apple Watch, but not without strict guidelines from Apple.

Apple advises developers to create images that will present well on both Apple Watch displays, otherwise they will have to create separate images to match each display size and resolution. Apple has also given specific sizes for various icons on the Apple Watch models; the smaller watch should have a Notification Center icon that is 29 pixels, a long look notification icon that is 80 pixels and a short look icon that is 172 pixels. The larger Apple Watch should have a Notification Center icon that is 36 pixels, a long look notification icon that is 88 pixels and a short look icon that is 196 pixels. Developers can find resources and details about producing for the Apple Watch here.

Developers are also asked to create for the Apple Watch in accordance with Cupertino’s vision for the device that it be simple and “lightweight” with easy accessibility for brief and frequent use. Apple has called the Apple Watch its “most personal device ever.” In addition to the two size models, Apple will also offer three design collections, the Apple Watch, Apple Watch Sport and Apple Watch Edition, which will have different band options including stainless steel, silver aluminum, 18-karat yellow gold, space black stainless steel, space gray aluminum, and 18-karat rose gold. The Apple Watch will feature 11 watch faces, including a traditional analog faces and other more complex faces.

The Apple Watch is expected to launch in early 2015 stating at $349. The device will be compatible with handsets running the latest version of iOS 8, including the iPhone 5, iPhone 5c, iPhone 5s, iPhone 6 and iPhone 6 Plus.