7104-164 4" 16R Double Square, reads 32nds, 64ths, 50ths, 100ths.

This is my second PEC square. They are well made and accurate enough for my needs.

absolute necessity for high tolerance aircraft structures work

Perfect, exactly as described. Has machined ends ... Not cut off by a hacksaw, like other lesser brands at the box stores.

Product is square and true, locking nut is a pain. Tends to stick when locked - even with minimum force - and can be a pain to loosen.

a super handy layout tool if you do fabrication work

I got a couple of these double squares for reselling and found them with very good quality and probably last a lifetime with normal use. I will definitely buy again.I

I picked up this four inch one and a six inch figuring I would misplace them. They are so small they look like toys, but for regular use they are great tools. I thought they might be too small for "real" use, but was mistaken as I use them on a reglar basis for fine wood work. Both appear square using the old mark, flip, and mark technique (place on a straight edged piece of stock, draw a line, flip tool over and mark from flipped edge -- if they are parallel, it should be good enough for wood). The price is certainly a deal, considering US made and solid construction. Recommended.