These are quarter sawn oak plug bushings for wooden movement clocks. 
These were cut from 200 year old oak floorboards  reclaimed from Eli Terry Junior’s house in Terryville Connecticut. Oak clock bushings could not be made from a better source! 
These plugs are 3/8” in diameter. One plug can usually be used for multiple holes if they are installed properly. 
These plugs go along with the grain of the wood, cut with a special drilling tool. 
You are buying 30 plugs per purchase. Please contact me if you would like to purchase more.