HARDELL Digital Caliper, 6 Inch Stainless Steel Caliper Measuring Tool with Large LCD Screen, Electronic Micrometer Caliper Digital Inch/Millimeter Conversion, Automatic Off(Ruler & 2 Batteries)

Most of the whoop frame manufacturers have something like this on their page. It’s what we have used to make sure the lipo fits for years now. Either that method or some calipers and reading the dimensions of the battery from the sellers website

Measure with calipers, I guess? https://www.amazon.com/HARDELL-Electronic-Micrometer-Millimeter-Conversion/dp/B0BNCXJ1JD/