Based on the same concept as the Gravelking and Gravelking SK models, the EXT version incorporates the same ZSG Natural Compound technology, which creates a softer compound that is overlaid with a harder compound on the outside for increased durability.aX-Alphacord technology uses the highest density, flattest fibers possible for flexibility, lightness and increased puncture resistance. This durability is further enhanced by the Anti FlatCasing coating across the entire surface of the tire, which again increases puncture protection. The thick tread pattern is specially designed to perform at its best in mud and poor conditions. Tubeless ready. Product code Size ETRTO Tread Color Sidewall color Weight(g) Recommended inflation pressure(kPa) Recommended inflation pressure(PSI) RF733-GKEXT-B 700×33C 33-622 Black Black 330 MAX 400 MAX 60 RF733-GKEXT-D 700×33C 33-622 Black Brown 330 MAX 400 MAX 60 RF735-GKEXT-B 700×35C 35-622 Black Black 380 TLC: MAX 400/TUBED: MAX 525 TLC: MAX 60/TUBED: MAX 75 RF735-GKEXT-D 700×35C 35-622 Black Brown 380 TLC: MAX 400/TUBED: MAX 525 TLC: MAX 60/TUBED: MAX 75 RF738-GKEXT-B 700×38C 40-622 Black Black 430 TLC: MAX 400/TUBED: MAX 525 TLC: MAX 60/TUBED: MAX 75 RF738-GKEXT-D 700×38C 40-622 Black Brown 430 TLC: MAX 400/TUBED: MAX 525 TLC: MAX 60/TUBED: MAX 75