The Yale Door Closer 3301 is constructed of a cast aluminum alloy. It is considered a Grade 1 Closer, which is the highest grade possible. The closer features an adjustable spring tension, and separate closing, latching and back check intensity valves. The slim line plastic cover is standard on this closer. This door closer replaces the older 3301BF closers. The new version is Barrier Free Complaint. The hole spacing is 3/4" x 12", the cylinder is sometimes cast 20-3301-1001 on the back of the cast aluminum cylinder. This closer ships with all of the mounting hardware and parallel arm bracket.