Glarks 200Pcs 1/8" x 3/8" Aluminum Body Steel Mandrel Dome Head Blind Rivets Set for Sheet Metal, Automotive, Railway, and Duct Work

I have two 1/8" aluminum bars that I need to attach for a total thickness of 1/4". Should I use the 1/4" or the 3/8" grip length rivet?

Are these rivets all aluminum including mandrel or do they have a steel mandrel?

Flange diameter

What's the actual grip range. From diagram the physical length is 15/16, NOT the grip length. The grip length would be some smaller amount. 5/8-3/4?