The foam is around 3.5mm in thickness and fits between the plate and the PCB. 

Compatible with YMD75, BT75, KBD75, tofu84, D84 and others. (Milage may vary)

Notice

If you use Clip in PCB stabilisers, you don't need to adjust the foam. If you use screw-in PCB stabilisers, you will nee to cut the foam as shown in the red box.