Set of 12 (3x4) bumpers includes: 3 pieces measuring about 0.38" diameter x 0.35" height (with 0.13" diameter center hole) 3 pieces measuring about 0.38" diameter x 0.21" height (no hole) 3 pieces measuring about 0.38" diameter x 0.16" height (no hole) 3 pieces measuring about 0.38" diameter x 0.13" height (no hole) Commonly, two front bumpers are fastened underneath the toe-end of the treadle and one rear bumper is fastened underneath the heel-end of the treadle. Alternate bumper heights allow you to customize the fit and feel when stepping into the footswitch or rocking back to a maximum open treadle position.