Rubber base attached to the bottom of the bag.  This double layer (one internal one external) allows more elevation adjustment without bowing the base if you pump it too far, and the rubber on the outside gives the bag traction so it really stays put under recoil.  
 
It also has a handle made of 2" reinforced webbing, which makes it simple to grab with a finger or 2, when getting all your gear off the shooting line in a hurry.  
 
The Endgame comes prefilled and sealed, with a new media that is very aggressive and holds its shape under recoil, requiring very little effort to get back on target. 
 
With no air in the system the bottom of your stock or ABR will sit 3" above the shooting surface and can inflate to 4.25", all while being rock solid stable.  
 
Endgame Bag instructions,
Position the bag with the handle to the rear if you are right handed and to the front if you are left handed
Use the bottom of your stock to make a channel down the center of the bag, for it to glide in. Start with no air in the pump, adjust your bipod to get everything at the right height to get as close to the target as possible before adding air to the system.
Add rubber pads under the bag if you need to raise it up, don't inflate it too far, the best stability is with the least amount of air in the system.
Now go out and set some new personal bests and win some matches! Enjoy!