Ø 1-1/2", black, fastening by screw* ( not supplied ) , allow 10 to 12 foot pads by sled, that is to say 5 or 6 foot pads by runner to have a minimum non-slip surface.
BE CAREFUL ! If you maintain your wood sled with oil of linen, these pads hates the oil of turpentine because this oil alters plastic used for these pads and they become brittle.
* Stainless steel screw 4 x 12 or 4 x 16 m/m.