These are the knobs sold with the Thumler's Tumbler Model B. They are sold in a pack of 6 knobs. Both tumblers require 6 knobs to secure the lid. Thumler's size is 1/4-20 female thread and the Rebel size is 6mm-1 female thread. Make sure you select the correct thread you desire. These are free spinning fluted anti vibration knobs.