Material:
Screw in tempered steel, ball in ball-bearing steel
Surface finish:
Black screw, quality class 10.9;
ball hardened, natural finish
Note:
Form A with full ball is used when a clean, polished pressure surface is required. Surfaces which are not plane and parallel can be firmly clamped or supported with form B with flattened ball because the movable ball can adapt itself up to 9°.