The Tell CL100006 Satin Stainless Steel Storeroom Lockset is a heavy duty commercial storeroom ball knob. UL listed - 3 hour fire door. The Keying features are a 6 or 7 pin SCC keyway with 2 nickel keys per lock. Door range is 1 3/8-inch to 1 3/4-inch. Standard 2-3/4-inch backset and standard T strike (1 1/8-inch x 2 3/4-inch). This is made out of cylindrical steel coated with zinc dichromate (corrosion resistance). Outside knob is always fixed.