Mounting attachment for the T-1000 holster. The most common mounting plate (included in T-1000 package) is the Blade-Tech 3-hole, small -T-Plate.
The longer, larger T-Plate is the Safariland, G-Code and Double Alpha pattern. Many holsters will allow you to mount it using this pattern even if you are currently running the Blade-Tech T-Plate. The advantage of the longer T-Plate is more rigidity for single layer (thinner) Kydex holsters.