1. Based on the item in the link https://dmleatherstudio.com/products/brown-leather-apple-airpod-pro-case?_pos=1&_sid=adf3bc951&_ss=r&variant=32073125429313
2. Fit for the FOB in size below
1- 3/4" wide (left to right) ---4.4cm
1- 3/8" depth (front to back) ---3.5cm
3-7/8" high (top to bottom) ---9.8cm
3. Add a loop on the backside for belt to slide thru 1-5/8" wide belt，the belt loop should be 1 full inch higher on the case.
4.The top to pull over tighter, so there is no slack or loop.
5.Stitch up the bottom to make it tighter.