This steel sling hook is quite legendary for such a small piece of equipment. Made by Tacticaltrim from Germany.

The sling hook allows you to mount a 25 mm / 1" sling or webbing to a small eyelet as seen on many HK rifles and others. It has a stamped steel gate to prevent unintended opening and an extra hole that you can use to connect another hook and turn a 2-point sling into a single point.

Several manufacturers make this kind of hooks under different names but most commonly these are called HK Hooks or Clash Hooks. Watch out for die-cast zinc knock-offs, the hook can break rather easily on those even if your rifle isn't particularly heavy! This Tacticaltrim hook is made of proper steel and is suitable for hard use.