SAN FRANCISCO—At a press event near Microsoft’s Build developer conference, Nokia offered the chance for a select few to lay hands on the company’s upcoming additions to its fleet of Windows phones: the Lumia 930, 630, and 635.

The 930, advertised as a new “flagship” phone, is a bit of a cheat, as it’s essentially identical to the Lumia Icon now on sale through Verizon in the US (albeit with different radio parts) and won’t be sold in the US. That makes Nokia's entry-level Lumia 630 and 635 phones the first Nokia Windows Phone 8.1 devices to arrive in North America.

The 630 comes in two versions for GSM 3G networks and is primarily targeted at the international market—a $159 single-SIM phone and a $169 dual-SIM variant which will allow users to use two numbers on the same phone. The Lumia 635 will be a 4G LTE phone that will be sold worldwide. It arrives in the US in July and is priced at $189 before carrier subsidies and taxes.

In our brief time with the phones, the 635 looked like a low-end but worthy emissary, aimed at building on the success of the Lumia 520 while adding a splash of color—literally. While many of its components are last year’s news, the 635 does come with some interesting new technology, an iPhone 5C-like capacity for customization, and a street price that will be comfortably below $100 for US customers (if they’re subsidized by carriers). And while the Lumia 630—the 635’s 3G GSM look-alike—may be intended more for the global market than for the US, it could also find a home here as a prepaid plan smartphone.

The 630 and 635 both have a plastic external body that can be popped off and swapped out. Bodies come in white, black, and DayGlo shades of orange, yellow, and green so you can color-coordinate your Lumia with your mood (or, if you’re Stephen Elop, with your sneakers). The phones both felt light but sturdy in my hand.

Popping off the outer body provides access to the phone’s battery, SIM card slot, and its mini-SD slot. The 630 and 635 can accept mini-SDs up to 128GB to supplement their internal storage of 8GB. The 635 is supposed to get up to 12 hours of talk time off its 1830 mAh battery, but it doesn’t hurt to be able to swap in a fully charged battery.

The 635 and 630 are each powered by a 1.2GHz quad-core Qualcomm SnapDragon 400—not the fastest processor on the market, but similar in compute performance to the A6 chip in Apple’s iPhone 5C (and considerably more powerful than the Lumia 520’s internals). The screen resolution is OK but not astounding; the 4.5-inch screen has the Full Wide Video Graphics Array (FWVGA) resolution of 854×480 pixels. The 5-megapixel camera, though enhanced by Nokia’s software, also underwhelms.

However, the 630 and 635 are the first phones to ship with Nokia’s SensorCore technology, a software interface that allows an application to access accelerometer data even while the phone is in standby mode. Nokia demonstrated this feature with a Bing fitness application that used accelerometer data to act as a pedometer, counting all the user’s steps.

Aside from the sensor technology and the price, the most notable differentiating feature of the 630 and 635 is that they are Windows 8.1 Phone devices and will ship with the Cortana voice interface, storage and power management tools, and all of the other features of Windows 8.1.