Precision Reflex 6.8mm SPC Straight MSTN QC Brakes. The brake is machined from stainless steel for heat resistance. Specs: 304 Stainless, outer diameter 0.95 in, length 2.0 in, threads 5/8-24. Straight brake with spacer shims included to set the timing. The three holes should align at the 1 o'clock position when tightened into place. Install with a round screwdriver in the first slot closest to the barrel.