9200 Spare part kit felt rings for 881/4/1 bit holder, 5 pieces 5x 9201 Felt ring for 881/4/1: 27 mmFor patio construction, the screws should be countersunk to be evenly flush with the decking. The 888/4/1 bit holder with variable screw depth limitation and felt ring allows for a uniform depth and protects the surface from brush marks. Two spare felt ri