If your car is 2018 or earlier, the boots listed in this section is for "Internal Fit" style and you should be in ordering from here. But if your car is a late model (like Camaro G6, Corvette C7, Subura STi 2018+ etc., the boots might be an External Fit style which IS NOT COMPATIBLE with those internal fit boots listed here, nor are those non Brembo calipers (such as Corvette Z06 made by PBR).
Dust boots listed in this section "Select by Piston Size" is good only for internal fit.
For example if your pistons has 38mm in diameter, then DB-38 is good for you, but if you have external fit boots you must add 3mm to the diameter i.e. DB-41 should be the one to order. In general even number is for internal fit, odd number is for external fit.
Dust boots for the following calipers have external fit boots so it's more assured to order from the car make to avoid ordering by mistake.