It fits the triple chainring on the Mongoos Envoy, without interfering with the front derailleur. It also has a secondary benefit of making it impossible for the chain to fall off the right side of the big ring, which used to happen from time to time. 

The bolt pattern is quirky, so no telling what other cranks it might fit. 

I printed in PETG because that's what I always use for things that might be outdoors or in hot cars. But PLA would probably work fine tbh.