When you're out on a ride the last thing you want is to be limited by your tires in any way. Surly's ExtraTerrestrial tires were designed to let you ride without limits by following a simple tenet for tire design: make 'em high-volume and kick-ass. The ExtraTerrestrial tire was meant to serve as a heavy-duty off road touring tire that shines on hard pack surfaces. It uses a nylon breaker in the sidewalls for cut protection, a molded pattern for anti-cut propagation, and a Kevlar cap under the tread to protect against flats. The ET tire uses a distinctly directional tread pattern and its width yields more traction than you might expect from a tire with such little rolling resistance. The tread is low profile with a file tread in between blocks. The ExtraTerrestrial tire has enough width and traction for the soft stuff and won't bog you down on smooth or hard surfaces. It's made to be durable and versatile and is at home on tour or on the trail. - Bead Seat Diameter: 559mm - Casing: 60tpi, tubeless-ready bead (928g)