Surly says....The ECR fork is much like our Ogre fork. Both are CroMoly 29er forks. Both work with frames designed for 80m-travel suspension forks. Both feature 51mm I.S. disc calliper mounts, brake line guides, accommodations for a rack and fender, and 2 sets of cage mounts (one on each leg) that let you mount large size or standard water bottle cages. Both are designed to run just about any combination of parts and accessories you'd want on a fork and are finished in durable black powdercoat. The only real differences are 1) ECR is disc brake only, and 2) ECR's offset is 47mm (29" only), 5mm more than Ogre's.

Axle-to-crown: 468mm (447mm for 27+)
Offset: 47mm (43mm for 27+ fork)
Steerer: 260mm (29") 285mm (27+) , 1-1/8" straight
Tyre Clearance: 29 x 3.0"
Weight: 3.1 lb (1.4kg) uncut