Tech Tip #1
Have a mountain bike ride planned where there are lots of cacti? If you can't find sealant filled tubes I have an easy solution.
Find a suitable tube, preferable a new one that fits your size wheel. Buy a tube of sealant and a patch kit(there are several brands out there; Slime, Tru Goo, etc.). Poke a hole in the undeside of the tube (the side that will be on the rim not the tire). Insert the nozzle of the sealant container and fill the tube with the amount as directed by the manufacturer. Thoroughly clean the out side where you poked the hole and patch.
Unortunately you cannot buy pre-Sealed 29er tubes, so for the race I made some. Not only did I not have any flats during the race, I am still using the tubes and they are working perfectly!