Small tube rivets with a slightly domed cap.  Make sure that you use a concave anvil or the heads on these will get all bent out of shape.
Very sturdy – best set with a hydraulic or hand press machine.  Head diameter is 9/32″ (just over a quarter of an inch), shaft length is 7/32″ (just under a quarter of an inch),
and the tube outside diameter is 1/8″.  Good for joining a total of about 1/8″ of leather/fabric/stuff together.  Nickeled steel, silver color.
RVT-113  Sold in packs of 100 for $6.00  USA shipping included.