The service life of any opening is dependent on the ability of the hinges to maintain door alignment and smooth operation over millions of cycles. In a demanding application like a busy school or commercial building, the entrance may be subject to severe stress. Roton continuous gear hinges protect against early entrance failure by distributing opening and closing forces along the entire length of the door and frame. Rust–proof, high strength aluminum extrusions keep doors in perfect alignment while cushioned bearing blocks carry the heaviest doors effortlessly through years of opening and closing cycles. Standard duty models have bearings 5-1/8″ on center. Heavy duty models (indicated by the suffix HD) have double the number of bearings–spaced on 2-9/16″ centers.