Ball Bearing 15*10*4 - for Redcat Racing Vortex SS. Also compatible with: TORNADO BB, TORNADO S30, VOLCANO SV, VOLCANO S30, VOLCANO MX, TSUNAMI, VOLCANO STX, SHOCKWAVE, LIGHTNING STR, LIGHTNING EP DRIFT, TSUNAMI EPX, LIGHTNING EPX, TORNADO EPX/EPX PRO, VOLCANO EPX/EPX PRO, VORTEX EPX/EPX PRO, VORTEX SS