The Grimloc Locking D-ring was originally designed for the Department of Defense (DoD) by ITW Nexus. One of the original uses was to attach hydration systems (camelbaks) directly to their body armor/load bearing vest. The Grimloc was designed using Ghillie-Tex IR reduction plastic which resists rusting and corrosion. These locking D-rings are not to be used for rappelling, but for equipment attachment only. They attach to your LBV/pack/etc by threading behind the MOLLE/PALS webbing.
They are made of GhillieTEX, a polymer that is resistant to IR detection. Because they are plastic they are less likely to become a secondary projectile if broken. The area where the spring is for the push button (on the top in this picture) has purge ports to get rid of water and sand. The top of the push button (plunger) is textured for better grip with wet or gloved hands.
The Grimloc will break away at around 8o pounds of pressure as a safety feature so if the used gets caught on something his body weight will break him free.
I’ve found these to be very handy for many uses. They are light weight, but tough and can be used in any environment. I have yet to find anything negative about them, other than the fact that I keep finding places to put them and have to order more. Don’t use cheap carabiners that you find in the checkout isle of Wally World when for almost the same price you can get something of great quality. Honestly, it’s not even worth it with the prices of these now. If you need them, get the Grimloc Locking D-Rings.
Ben 
Smooth