Developed to hold 1/4", 8mm or 1/2" round shank bits, these are the same brass cup inserts we use in our showrooms for bit display. They mount in a 5/8" diameter hole, and have grooved shanks to provide a good mechanical glue lock if permanent installation is desired. The center bore measures just over 5/8" deep.
One advantage of using these holders for bit storage, rather than simply boring suitably sized holes in a block of wood, is that they act as barriers against wood moisture migration, protecting bit shanks from corrosion.
Made in Canada.