Tire casings refer to the layers used in order to construct the tire, the casing can be made up of a number of layers and will usually protection against punctures. Maxxis have four different casings options, however, not every tire will come in every casing:
EXO: A single ply casing option with a cut- and abrasion-resistant Exo material that offers additional sidewall protection. Exo casings areavailable in both 60 TPI and 120 TPI tires.
EXO+ : The guts are the same as the 60 TPI EXO casing but with abutyl insert added at the bead to prevent pinch punctures and rim damage.
DoubleDown (DD): Aimed at Enduro riders, the DoubleDown uses a dual ply construction made up of two layers of 120 TPI material in order to balance durability and suppleness. Large Butyl inserts extend from the bead and up the sidewall for pinch protection and added stability.
Downhill: The toughest tires Maxxis makes. It features a similar design to the DoubleDown but uses a heavy duty Dual-Ply 60 TPI casing for maximum durabilty.