It's too bad that the advertizing is so cryptic. They don't seem to know what they are selling ( sigh ).

It took me a while to figure out that the 48g weight retracts were about the equivalent of a .40-.60 size plane's retract.

The weight and the diameter of the gear receiver hole, is the tipoff to their sizing.

I'd also advise anyone considering the NP or HK retracts to carefully measure their plane's retract areas and assure that the ones being purchased WILL fit.