This is a hand-made removable beaver tail.
This model is reversible: clean on one side with a D-ring, and a with a patch
panel and zippered access on the other.
It has two 1.5" straps on the bottom with 2" spacing between them. Pass these
straps through triglide buckles on you backpack. Remove side release buckles
from compression straps of your backpack and pass that straps through buckles
that come with the tail.