Atibal Rifle Scope Bubble Level for 30mm tube Black. A good way to verify that the Rifle Scope on your weapon is appropriately level the Atibal Rifle Scope Bubble Level for 1" Tube BSL1 is an effective device for ensuring the accuracy of shots that have been shot using a firearm with a 1" tube. For a good way to make sure your weapon is properly level pick the Atibal Rifle Scope Bubble Level for 1" Tube. Specifications for Atibal Rifle Scope Bubble Level for 1" tube: Product Color: Black Package Contents: Atibal Rifle Scope Bubble Level for 1" tube Atibal AT-RBL-30m: Rifle Scope Bubble Level for 30mm tube Black