If you look at a T-Type rear derailleur from Sram from behind, the rear derailleur cage is bent outwards. But how much curvature is there ex works, or is the rear derailleur bent? This question is difficult to answer with the naked eye, but that's where Leap Components steps into the breach.

The Dutch supplier specializes in 3D-printed parts that simplify and enhance the handling of Sram components. The part, called Alu Cage Check, can be attached to the aluminum transmission derailleur and shows exactly whether the lines and angles on the cage are still correct - or warped. This can be a real help in the workshop if the derailleur cannot be adjusted at all.