This is the Schlage SC20 6 pin bump key. This bump key has been cut to the deepest factory specifications, and thus uses the pull back method for bumping. The Schlage SC20 key is the “master keyway” for Schlage. Schlage makes a number of different key ways, and you need the correct bump key for each, but the SC20 key will fit into any Schlage keyway. The reason I still sell the SC1 and SC4 keys, is that the SC20 key is a much thinner key, and is prone to breaking after much use. You should have this key in your set, but try your other Schlage keys first. This is one of the most common brands of key in the United States. This key is typically cut from Brass alloy, but could be cut on Nickel or just brass depending on stock.