This is a hand-made removable beaver tail, not the OEM one.

Good for winter clothes, rain gear, boots, helmet, food bag and so on.

Fits GR1, Rucker and GR2 models.

You don't have to modify your backpack.

On the bottom it attaches with 4 straps and buckles to molle/pals rows on your backpack. It can be positioned higher or lower. The bottom straps are adjustable.

On the sides it attaches to side molle/pals through  removable and adjustable side-release buckles.

On top it has a long strap with side release buckle and it attaches to carry handle. Everything is adjustable, all buckles are removable.