RENTHAL 420 Chain and sprockets conversions coming in stock now ! With close collaboration with our major Sponsor 'RENTHAL' we can now offer a fantastic weight saving idea for your GG Pro. With the superb quality of the RENTHAL R1 Chain we have found that their 420 sized chain is more than strong enough to cope with bikes up to 250cc under 'normal use'. The superb quality R1 420 Chain is actually stronger than most 'normal' quality 520 chains on the market! The biggest advantage of using the 420 Chain and sprockets conversion is the OVER 500 GRAMS (0.5KG) of weight saving !! Also with the PRO125 the usual preferred gearing of 9 x 48T actually does not work 100% efficiently...A 9T 520 front sprocket affects the running of the chain (cyclic variation) and can also make the bike stall quite easily. We have found that using the new 420 chain on an equivlant 11T 420 sprocket runs ALOT better which helps the running / spinning of the rear wheel and so helps performance and helps prevent stalling. The rear wheel runs alot more freely and helps with the relatively low power with a 125cc. This 420 chain and sprocket conversion has been thoroughly tested in various conditions on Kevs own 225cc machine and also on a 250cc machine in various conditions. FOR PRO125 --- The preferred 520 sprockets are 9 x 48. The equivlant in the new 420 size would be 11 x 58. FOR PRO250 --- The preferred 520 sprockets are 10 x 42. The equivlant in the new 420 size would be 12 x 50 Also the physical size of the new 420 sized sprockets are significantly smaller to help clear rocks etc. This is a fantastic idea which WORKS very well. You have just got to trust the smaller 420 chain.