A half cylinder is a single-sided Euro profile cylinder: it takes a key on one face only, with no key or thumbturn on the back. The Ilco half cylinder is machined from solid brass bar stock and is used in European style mortise locks, the kind common on aluminum storefront and glass entry doors. If you need key access from both sides of the door, a half cylinder is the wrong part, you want a double cylinder instead.

Cam position is 2 o'clock on this cylinder, meaning the cam sits offset from vertical when the key is in the neutral position. European mortise locks and storefront hardware are built expecting a specific cam orientation, and the wrong one will not drive the lock's follower correctly even though the cylinder will physically slide into the profile cutout. Confirm what your lock body calls for before ordering.

Four Schlage keyways are offered: Schlage C, Schlage E, Schlage F, and SX. If your building is already running Schlage C, which is the most widely used of the group, the cylinder can be pinned to the same key. Order it keyed alike if you want multiple cylinders on one key, or keyed different if each opening gets its own. The cylinder is rekeyable, so it can also be repinned in the field later.

Both pinnings are available. Six pin gives you more key change combinations, which matters if you are building or extending a masterkey system across a property, and it has to match the pinning of the rest of the system to key alike with it. Five pin is the simpler choice for a standalone opening. Match whatever your existing keys are cut to, a 5 pin key will not operate a 6 pin cylinder pinned as a 6.

Three finishes: bright brass (03), satin brass (04), and satin chrome (26D). Satin chrome 26D is the usual match for aluminum storefront doors and brushed stainless pulls, while 03 and 04 pair with brass entry hardware. If the rest of your openings run a finish outside those three, Ilco quotes custom finishes.

The chamber caps use M4 x 0.70 set screws, 6mm long. That is the detail a locksmith needs when servicing or repinning the cylinder, since losing one during a rekey means sourcing a metric set screw rather than anything out of a standard imperial kit.

This is a commercial-duty replacement part, built from solid brass bar stock for storefront and European mortise lock applications rather than residential use. Property managers standardizing a run of storefront entrances can order all openings keyed alike in one keyway and finish.