Slightly smaller than expected but the description is correct. The mounting slots are 1/4" and it comes with small t-nuts and bolts. I think I just assumed it was 3/8", but that doesn't matter. In any case, this isn't a vise for large workpieces so I doubt they are the limiting factor There is always some buoyancy with this type of grip but the tracks are perfectly aligned and as far as I can measure straight Came packaged in an absurd amount of lube.