Review on Advanced Precision Machinist Milling Machine Test, Measure & Inspect Kit by Dave Russell

At first glance they look like block 123, but the unthreaded holes don't accept 3/8 screws, so you can't use them like block 123. Someone really messed it up when designing it. YouTube video search on Chinese 123 blocks. There is a very experienced machinist who explains why they are useless. Spent a lot of time and money on this, very disappointed. The steel is hardened so you can't fix mistakes, basically just a paperweight.