The Pitbull barrel support is designed for the customer that loves to tweak their Benjamin Bulldog to get the most accuracy possible.
The 4 pack of supports are designed to be pushed onto the barrel at any interval you like, and hold the barrel tight and rigid to the barrel shroud. 
It can help reduce the vibration or wobble of the barrel as the bullet travels down it. Our tester reported a 1/4 MOA reduction of group sizes with a variety of bullets and shooters.