GBU, or Gas Block Utility, was created to provide a sturdy and compact platform for users to install / remove gas tube pins on low profile gas blocks, and install / remove gas block pin on the barrel.GBU's circular lines below and rough texture inside the gas block cavity are by design, lest anyone should think they're tool marks, these take machining time to put in place. Whereas it would have been good enough to have consistent surface throughout the GBU exterior, we put in thoughtful and useful touches. The textures are one of them, the other is the finger access relief access above and below the gas block cavity.Features Rebated bottom for using a vise to secure the platform. Textured bottom to limit sliding on the workbench. Textured gas block cavity to reduce gas block movement inside the GBU. Blind hole slot to capture gas tube pin. Wide gas block cavity allows gas blocks up to 1.19" long (Crane spec gas block is 1" long.) Machined from a solid block of 6061 and anodized light green, it's 3.35" (L) x 2.45" (W) x 0.94 (H), it weighs 7.52 oz. Gas block cavity is bi-directional, i.e. barrel with gas block and gas tube can be seated on GBU with the muzzle facing left, or right. Left side accommodates gas blocks with barrels diameter up to 0.855. Right side barrel cavity is smaller, and accommodates barrels up to 0.760 diameter. Proudly designed and made in the USA.Please NOTE: GBU is compatible with low profile gas blocks. It is incompatible with TDP spec front sight post/gas blocks, or any adjustable gas blocks.