Review on Ultra Precision Plastic Blocks 0.0001 by Ralph Gerry

At least 0.0005 inch accuracy - perfect for hobbyists At least 0.0005 inch according to my Mitutoyo Digimatic caliper (same resolution). Both sides have the same dimensions on all parallel sides. While I didn't specifically measure the parallelism, since measurements in several different areas all showed within 0.0005 inches, it's safe to say that both blocks are parallel to within that degree. Pros: - Fairly accurate block pair, 0.0005 inch in all measurements. .- Quality body for blow molding. - Fasteners and an Allen key are included for installation. - Comes with oiled paper finish to prevent rusting. - Price. - Protective oil is thick and sticky and can be removed with little effort. - One of the bolts loosened during transport rattled in the hull. It's hard to beat the price per dollar here. Accuracy isn't lab-level, but good enough for a workshop or garage - adjust expectations accordingly.