I opted for the Hanger 9 150 P-47 retracts for mine. They each use a servo that attachs directly to the gear itself. I have read they hold up very well to a grass field and are a lot cheaper than they Century jet or Sierra gear. Early in this post they were used in this plane and I e-mailed the user and he said they worked out very well on this Zero I'll post some pic's as I build