? For larger and heavier work. Made in numbered pairs from mild steel. Set consists of two blocks and one clamp. Blocks feature two clamping grooves. Lower grooves permit blocks to be clamped to table. Dimensions: 2?1/2 square 3 long. Work capacity of approx. 1/2 to 2?1/2 diameter. Accuracy: Sides are square with each other within .003 . Ends are square with sides within .003 . V groove is parallel and central with sides within .002 . V groove is 90? 1/2?. V s of pairs are central and parallel to each other within .004 .