The '35' part is a reference to its astounding width, which gives any wheel built with it a larger footprint, and so, more traction. Very useful for cross-country and all-mountain riders who are looking for lateral stiffness without so much weight.
These rims can be run tubeless with the use of Velotape.
Specs
Rim Size: 27.5"
Width: 35mm
Height: 22mm
Optimal Tire Width: 50mm - 70mm
Tire Interface: Clincher / Tubeless
Valve: Presta 32 - 40mm
Bead Seat Diameter (BSD): 584
Effective Rim Diameter (ERD): 558
Weight: 555g