We wanted to refine our flat top receivers to make mounting the scope rail as solid as possible. So we redesigned the top to include a groove that accepts our new rail and once it's bolted on is so solid it's almost like the integral rail version. Instead of making 4 different rails (0, 10, 20 & 30 MOA) we now only offer two, a 0 & 20 MOA. Between these and the internal adjustment on most scopes, it is enough for 99% of all shooters to zero in on their objective target.

Linky :

https://dlaskarms.com/product/tuf-22-receiver-flat-top/