These pins are commonly used in table leaves to ensure correct alignment. Both pins and sleeves fit an 8mm (5/16") hole.
The pin is steel with a brass wash finish. The sleeve is turned brass and is drilled slightly oversize to allow some play for easy pin entry, and to compensate for wood movement in the leaf. 8mm in diameter by 21mm overall length.
Sold in packages of 20 pins and 20 sleeves.