This thing adapts a mini sized Estes Model Rocket Engine (i.e. size "A") to a standard size (e.g., size "C").

Printed on Makerbot 2 with "medium" settings
10% infill
2 shells
0.27 layer
50mm/s speed while extruding.

Print time = 27min.
Weight (without engine) = 6g

This mount allows the use of the smaller "mini" engines in rockets such as thing:87495 which are sized for the larger "standard" engines.