Ok..
LA243 are the original mid arm.. which you bought or got with the first " worlds kit " upgrade on the RB5 these had 3 holes for shock mounting
I think these came original with the ZX5??? so you got one rear arm and one lazer front arm.
UM521 was the mid arm for the RB5 came with RB5SP same as above but with only 2 holes for shock.. the 3rd hole is the one nearest the hub.. on this you got a rear arm and an RB5 front arm.
UM521-1 That came with the RB5SP2 and the UMW517 upgrade kit which including the motor spacing option etc.. this only has one hole in the wishbone for mounting the shock, this hole is situated inbetween the 2 holes on the above wishbone..
LA272 this is the newest out and this has the same arm as UM521 with 2 holes but comes with a LAZER SP/FS/FS2 front wishbone..
LA255 is the standard arm that came with the FS kit i think, slightly shorter but in the pack you get a lazer front arm for SP/FS..
I think this is all right...??
Hope this helps..
Cheers
Nick
