Rhom air is no longer in buisness so parts for the gear are not available unless you can find suitable alternatives those gear look like a money pit there also set up for brakes which require more plumbing, that = more areas for leaks, and problems.
if your looking for retracts spend a few extra $$ and get a new set you will avoid alot of the hassles that leaky seals and old hardware provide.

several popular types available are,
spring air http://www.retracts.com/
century jet http://centuryjet.com/index.php/cPat...17a20134f43a2d
Robart http://www.robart.com/
shindin machine http://www.shindinmachine.com/
LADO http://www.lado-tech.net/ there electric actuated

the only type I don't own is shindin machine,and spring air, shindin are mostly geared for giant scale models and I fly mostly 60 size planes the others have there advantages and drawbacks.
theres a few more out there use google.