I have a few, I also have 300x21. One is on its way to you FOC for services to VMX.
If you are going to race the bike at Nepean or Barleigh Ranch the IRC 300x19 Farm Knobbly is a far better choice. Distributed by Ficeda, Yamahas Accessory Division, IRC should be available at any Yamaha shop,
Trust me they work good,
Don't run the Midas Speedway on the front they walk too far off line,