Fowler Sine Bar equipment used with gage blocks is highly recommended for securing a high degree of accuracy in measuring angles for grinder and milling machine set ups. Both sine and rolls hardened and ground for extreme accuracy. Features: Top surface is accurate to .00003" per inch of length. Parallelism: .0004". Flange on end of Bars and Plates for resting work. Both Sine Bars and 5" Sine Plates have holes for mounting/clamping. Includes fitted case.