Special Tool?

Can anyone tell me the tool used to remove these Intrepid/ IPK caliper piston caps ? Have been unable to find a special tool and a 15mm Allen socket is a hair too large. Have not tried a Torx fitting yet but would need to order one to try it. Would greatly appreciate any help. This appears to be an RK/2 caliper with 30mm magnetic pistons, if that helps. Thanks !