Sharkfin Racing chain guard, keeps your fingers from getting into the rear sprocket and chain in the event of a crash - as required in the rules for racing.
You could find some material, measure and draw up a shape, cut it out, drill some holes and make your own - many do. We have a lot of bikes we need to fit them to, so we drew one up that covered every bike we could measure up, and had them laser cut in lightweight aluminium.
Save yourself the hassle and pick up one of the Retro Moto Racing Sharkfins for your race bike! Slotted mounting holes already cut out, just affix to your swingarm and you are done. These do sometimes break in a crash, so its worth having a spare in the race kit, we've provided a few of these to racers at the track for last minute scrutineering purposes, dont get caught out without one!