Petzl Bolt HCR Bolthigh Corrosion Resistance Stainless Steel 12mm Pack of 20 P36GH 12. This 12MM product comes in an economical 20-pack so you'll always have plenty on hand. Designed for highly corrosive environments the HCR 904 bolt features a large attachment hole for easy clipping. It's big enough that you can install two thick carabiners at the same time in fact. The hanger's thickness teams up with the attachment hole's rounded edges to minimize wear on connectors made of any material. An anti-rotation system helps keep the hanger from turning while the anchor is being installed or when it's heavily side loaded during use.