I ordered the G12 5,5 coupler with bulkheads not long ago; they arrived in a very timely manner; much quicker than other G12 vendors. Unfortunately the coupler does not fit the 5.5 airframe; it is slightly larger. It would take a tremendous amount of sanding to get everything to fir properly. The quality of the coupler and bulkheads are just fine but it's very difficult to get compatibility of airframe/coupler sizes among different manufacturers. There are just enough differences in specs to make fitting problematic. However; I will hang on to the coupler until I can find an airframe that is compatible.