'SATGURU' Steel V-Blocks are made of tool steel, hardened, tempered & precision ground on all sides. Both sides 'V' with one clamp1. Unbreakable Steel Clamp.2. All Hardened & Tempered 52-56 HRC.3. Parallelism & Squareness of all faces & V within +- 0.005mm.4. Inspection certificate is furnished.