The 5th. photo shows the difference between the Weaver-compatible mount on the dot sight and the M1913/Picatinny mount with the rectangular locking lug inside the bottom next to it, that lug is too wide to fit into the slot on this adapter.

This adapter is made from aircraft-grade 6061 aluminum, the screws are grade 12.9 metric/12 US. The screws should be torqued to no more than 12-15 inch-lbs. I say 12-15 because torque wrenches tend to vary a little in calibration, if 12 doesn't hold firm enough you can go up to 15. I use a Fat Wrench and 15 is the absolute max, 12-13 holds perfectly firm. If overtightened a slight bulge will develop just above the screw head that may need to be filed flat again for your sight mount to fit flush.

It's extremely difficult to find an adapter that allows a standard dot sight to be mounted on a Crosman Steel Breech. This adapter works with any Weaver-compatible dot sight. Most dot sights are either sold in Weaver-compatible versions or have removable Picatinny mounts that can be converted to Weaver mounts that are widely available in the correct footprint for your dot sight. The UTG and Vortex Venom sights in the photos fit the Doctor/Vortex footprint, the Shield fits the Shield footprint.