1/4" BSF Round Head No Slot Screws / Threaded Rivets / Bolts. 1/2" - Fully Threaded. 5/8" - Part Threaded (3/16" Plaint Shank). 1" - Part Threaded (1/4" Plain Shank). 1 1/4" - Part Threaded (5/8" Plain Shank).
eBay