OTK (Original Tony Kart) brand wheels are the highest quality available.  OTK’s MXC wheel is recognized worldwide as the absolute best kart wheel there is.  Many manufacturers have tried to replicate the quality of the MXC and failed.  In fact, many teams will use the MXC instead of their own OEM wheels.  The MXJ is OTK’s brand new wheel introduced in 2015.  It is an extremely low-volume wheel which means you can start on higher pressure because you will not see as much pressure gain over the course of a race.