Leaker Majin Bu has details on what is possibly the battery of the upcoming iPhone 17 Air, the new ultra-thin iPhone that Apple is rumored to unveil this fall.

Bu states that the battery has a capacity of 2900 mAh, which, for reference, is smaller than both the 3582 mAh of the iPhone 16 Pro and the 3561 mAh of the iPhone 16. The 17 Air’s smaller capacity isn’t surprising, considering that the phone is rumored to be noticeably thinner. And while the 17 Air’s capacity is similar to that of the iPhone XR (2942 mAh) from 2018, drawing any conclusions based on the XR’s battery life (which was 11.24 watt-hours) isn’t relevant, since battery technology, internal components, and iOS energy efficiency have changed in the past seven years.

Bu also states that the battery will use a steel case like the one used with the iPhone 16 Pro. It seems likely that the steel case will be used throughout the iPhone 17 lineup to provide improved heat dissipation, higher structural resistance, optimized integration, as well as “higher charging powers,” Bu writes. In June, a report stated that the iPhone 17 could support the Qi 2.2 standard that allows for up to 50 watts of wireless charging.

Apple is expected to unveil the iPhone 17 lineup this fall. You can keep track of the upcoming iPhone with our iPhone 17 superguide.