123 blocks are essential precision tools for machinists, metalworkers, and workshop professionals. Use them for accurate setup, layout, and inspection tasks on milling machines, drill presses, grinders, CNC machines, and band saws. Verify 90-degree angles, check square alignment, calibrate fence cursors, and offset tables for precision work. Ideal for pre-welding and pre-assembly inspections to ensure parts are perfectly square. Hardened and precisely machined on all sides for reliable accuracy 23-hole design with 5 3/8″ 16UNC threaded holes and 18 untapped holes for flexible mounting Durable construction with no moving parts—lasts for years with proper care Suitable for setup, layout, inspection, and alignment verification tasks Essential tool for checking inside angles and verifying square accuracy Material: Hardened 45# Steel Hardness: HRC 48-58 Dimension: Approx. 1″ x 2″ x 3″ (L x W x H) / 2.5cm x 5cm x 7.5cm Height Accuracy: 0.0002″ Parallelism Accuracy: 0.0002″ Shape: Square Type: Gage Block Colour: Silver Qty: 2 or 4 x 1-2-3 Blocks as per your selection