These are antiqued brass-plated steel hollow post rivets, meant to be set with a splash anvil or a tool like the RS-0302 tool we sell on our Tools page.
Head diameter is 7/32″, tube length is 5/16″, tube diameter is 1/8″.
If you follow the Rivet Rule of Thumb these are best used for joining together 3/16″ of material or less.
RVT-127  Bag of 100 for $8.00, USA shipping included