Dytac Geissele Picatinny Rail Short. Real one to one scale of picatinny rail. Use #10-32 3/8 inch screw and #10-32 nut or can use #10-32 1/4 inch length scoket screw without #10-32 nut
#10-32 1/4 inch length socket screw
https://www.fastenal.com/products/details/1124038?term=%2310-32+1%2F4+socket
#10-32 3/8 inch length socket screw
https://www.fastenal.com/products/details/1123163?term=%2310-32+3%2F8+socket
#10-32 nut
https://www.fastenal.com/products/details/0149142?term=%2310-32+nut+black