This is a clamp on barrel bipod that will fit various sized barrels, which is made out of a high carbonate plastic. These can be used on high powered rifles to Air rifles, with one linear barrel. There is a small spring between the legs which provides enough clamping force to securely hold your barrel up. These are a great idea to carry in a backpack as they are compact and light, making them easy to pull out, once the game has been located. These are a great cheaper alternative to a Harris bi pod or other fixed bi-pods. Easy to fit and remove quickly.