This is a Surly’s mighty and over discussed Knard tyre.
A tread made up of low, closely spaced knobs, an effective tread for going fast over varied terrain. 41mm because it’s meaty enough to conform to the ground surface, absorb irregularities and provide a decent sized contact patch.
Bead Seat Diameter: 700c x 41mm
(622mm Bead Seat Diameter, 41mm casing width) (Note: 23–30mm recommended rim size.)
Casing: 120tpi with Kevlar bead (442g) 60tpi with Kevlar bead (680g) 33tpi wire bead (650g)
Price is for 33tpi – other types call the shop for pricing (2109225488).