binifiMux 20pcs M6 x 15mm Rivet Countersunk Socket Cap Bolts Screws Connecting 304 Stainless Steel

do you sell 20 mm rivet hex socket caps to go with this?

What specific grade/class are these bolts? (E.g., A2, Grade 5 or Class 8.8, etc.) Please don't answer if you aren't sure.

maybe I was unclear the hole the shaft of this nut to go into is it to large for a 1/4 size hole

Kindly advise if this is a 12mm head?