as z zee zed said lance, the uber ball drives have a weak point if you use a powerful engine,
if its anything larger than a stock g320 then use the strengthening rings that uber make,
the cups can crack/split on higher hp/torque engines
also they can wear the slots the balls run in sometimes ,
i'm running a set myself with a stock g320 without the rings, not had much run time on em yet though,
link to the rings ,
Radio Control Cars (uberrc.com)
if its anything larger than a stock g320 then use the strengthening rings that uber make,
the cups can crack/split on higher hp/torque engines
also they can wear the slots the balls run in sometimes ,
i'm running a set myself with a stock g320 without the rings, not had much run time on em yet though,
link to the rings ,
Radio Control Cars (uberrc.com)