Hello - The Assorted Rivets Kit includes 60 aluminum rivets and 60 steel rivets. These rivets are then separated in the resealable packaging into 25 each of 1/8" diameter with a 1/8" grip, 20 each of 1/8" diameter with a 1/4" grip, and 15 each of 1/8" diameter with a 1/2" grip. - Your Arrow Fastener Team
Hello - The minimum grip length would be .001 since the flange and the rivet bulge meet at the shear point. Arrow WA1/8 aluminum washers and WS1/8 steel washers are intended for use with soft materials such as fabric so the rivet bulge does not pull through the soft material. We recommend performing a test without the washer on your light aluminum. Use the washer on the back side of the thin aluminum if the test rivet pulls through. Hope this helps! - Your Arrow Fastener Team