Apple has yet to reveal how many Apple Watches it has sold but that doesn’t mean reliable data isn’t out there. Digital commerce research firm Slice Intelligence estimates that as of mid-June, Apple has sold 2.79 million smartwatches since its launch less than two months ago.

In comparison, manufacturers collectively shipped just 720,000 Android Wear devices through the end of last year.

We already know that the Apple Watch has the best profit margin of any Apple product. It’s also the first to include an interchangeable component, the wrist band, which according to technology research firm IHS, is a massive cash cow in its own right.

apple watch apple bill of materials smartwatch

Slice Intelligence estimates that about 17 percent of people that purchased an Apple Watch also bought extra band(s). The entry-level sports band retails for $49 which IHS estimates costs Apple just $2.05 to make. That estimate doesn’t include the cost of packaging and shipping but even still, it’s clear that Apple is making a hefty profit on each band sold.

Slice Intelligence Chief Data Officer Kanishka Agarwal said the black sport band is the most popular choice both for bands sold with the Apple Watch and separate purchases. Apple’s $149 Milanese loop band is the second most popular choice, suggesting many buyers are interested in both a practical sports band and a more luxurious option.