Which knee pads can I use with the P-40 pants?

You can use either 3D Tactical Knee Pads Cushion or Impact with your P-40 pants, but you cannot use both types of pads at the same time. 

Additionally, you can upgrade your knee protection with Solid Knee Pads to maximize your knee safety and comfort. These are inserted into a special pocket sewn onto the 3D Tactical Knee pads.