Correct 10mm is the thickest they will work on and yes the glass
IS 10mm thick
The included Rubber Spacer must be used between the Dry Side and the wall for thicknesses of 1/8” (3mm) and 3/16” (5mm). The Rubber Spacer is not needed for thicknesses of 1/4” (6mm) or 3/8” (10mm). Failure to use the Rubber Spacer can damage the pump, which WILL NOT be covered under warranty.