Fits 3.1" tube

Semroc Centering Rings 1/8 inch thick Plywood 29mm to T-3.1(2pk) SEM-CR-29mm-3.1P

Semroc Centering Rings Plywood 29mm to T-3.1(2pk) CR-29mm-3.1P 2 pack Made of 0.125" Light Plywood …

Semroc Centering Rings 1/8 inch thick Plywood 38mm to T-3.1(2pk) SEM-CR-38mm-3.1P

Semroc Centering Rings Plywood 38mm to T-3.1(2pk) CR-38mm-3.1P 2 pack Made of 0.125" Light Plywood …