GMS Mortise and Rim Cylinders: How to Read the Part Number

You have the old cylinder out of the door and need a GMS replacement with the right length, keyway, cam, finish and keying. GMS's catalog says all of these are built into the number, so a code such as M118SC10BATA2 can be read field by field.

How to read a GMS mortise cylinder number

The how to order table in the GMS catalog (PDF) lists the fields in this order: model, keyway, finish, cam and keying. The catalog's own example, M118SC10BATA2, breaks down like this:

• M118: mortise cylinder, 1-1/8 inch length
• SC: Schlage C keyway
• 10B: oil rubbed bronze finish
• AT: Adams Rite and Yale cams
• A2: keyed alike in pairs

Our titles sometimes put a dash before the cam code, as in GMS M100SC26D-ATA2, a 1 inch Schlage C cylinder in satin chrome. Some also add K2, which is not a field in GMS's tables.

Length codes: M156 to M112

The model code gives the type and the length. The model table on GMS's mortise cylinder sell sheet covers these lengths:

The catalog says extended lengths are available on request. The GMS website adds the M134 (1-3/4 inch), M200 (2 inch) and M212 (2-1/2 inch) and marks these three and the M138 as made in the Schlage C, E, F, C-K, C123 and C145 keyways only.

Thumbturn and dummy cylinders reuse the length codes with letters added, such as T for a thumbturn, TA for an ADA turn piece and D for a dummy. Their numbers have no keyway or keying field, and a dummy has no cam either. The catalog example M100T26DAR is a 1 inch thumbturn in satin chrome with an Adams Rite cam. The M100T26D-AT thumbturn and the M100D26D dummy follow the same pattern.

Keyway codes and pin counts

GMS lists 22 standard keyways and states that they are designed to meet the original manufacturer's specification. In the how to order tables they fall into three groups, each with its own keying codes:

• AW (Arrow 1179), CB (Corbin 60), KW (Kwikset 1176), SC (Schlage C), SE (Segal 9), SX (Schlage C~K), WR (Weiser E) and YA (Yale 8). Cylinders are drilled 6 and pinned 5, except the M156 and M100. Keying codes A2, KD and OB.
• CL4 (Corbin L4), RD1 (Russwin D1), SA (Sargent LA), SAX (Sargent LA~LC), SLB (Sargent LB), RA (Sargent RA), SCE (Schlage E), SCF (Schlage F) and YGA (Yale GA), in the M118, M114 and M112, and the M138 in SCE and SCF only. Drilled 6 and pinned 6. Keying codes A2-6, KD-6 and OB-6.
• A62, AST and ASV (Assa) and G23 and G45 (Schlage C123 and C145), in the M118 and M114. Keying code NK-6: sub-assembled with followers, no keys.

A2 means keyed alike in pairs, KD keyed different and OB zero bitted. GMS's general information page adds that its zero bitted cylinders are cut to a 1 bit or 2 bit depending on keyway and come with uncut keys for pinning.

For example, M118SX26D-ATA2 is a 1-1/8 inch cylinder in the SX keyway, and M118ASV26DATNK-6 is an Assa V10 cylinder of the same length that comes without keys. Our key blank guide explains keyways and key sections.

Finish codes

In the part number GMS writes the finish without the US prefix. The finish column of the cylinder tables gives 3 polished brass, 4 satin brass, 10 satin bronze, 10B oil rubbed bronze, 15 satin nickel, 19 black, 26 polished chrome, 26D satin chrome and 32D stainless steel. Some of our titles add the BHMA number, as in 626/US26D, and our finish codes chart pairs the two systems. In M100SC10B-ATA2, for example, 10B marks an oil rubbed bronze cylinder.

Cam codes and Adams Rite locks

GMS names its cam codes after lock brands, for example AR Adams Rite, AT Adams Rite and Yale, BE Best, CL Corbin, SA Sargent, SL Schlage and ST Yale. The mortise cylinder sell sheet notes that the M100, M118 and M114 include an AR and an ST cam, as on the M114SC26D-ATA2. The catalog also prints drawings of the CAM1, CAM2 and CAM3 cams, useful for comparing shapes with the cam on your old cylinder. For the cylinder an Adams Rite MS1850S deadlock calls for, see our Adams Rite model number guide.

Spare cams are sold on their own, such as the CAM1-AR Adams Rite cam. In the catalog, CAM1 fits the mortise cylinders (except the A62, AST, ASV, G23 and G45 keyways, which take CAM4), the mortise thumbturns and the MCM and YCM housings. CAM2 and CAM3 fit the other IC mortise housings.

Rim cylinders and IC housings

A rim cylinder number has no cam field. The R118 is GMS's 1-1/8 inch rim cylinder, ordered as model, keyway, finish and keying, with the same keyway groups as the mortise cylinders. The catalog example R118KW10BA2 is a Kwikset 1176 keyway cylinder in oil rubbed bronze, keyed alike in pairs. The rim sell sheet lists the R118 in 5 pin drilled 6 and in 6 pin, beside the R118D dummy, the R118T thumbturn and the R118TA with an ADA turn piece. Full numbers read the same way, as in R118SC26DA2 or the R118D26D dummy.

Interchangeable core housings have no keyway or keying field; GMS lists the cores as separate items. A mortise housing takes model, finish and cam: ICM6 and ICM7 are Best small format housings (6 and 7 pin), ICT6 and ICT7 their tapered versions, ICS the Schlage large format housing. The catalog example ICM726DST is an ICM7 in satin chrome with a Yale cam. Rim housings take model and finish only, as in ICR726D. For a 6 pin core in a 7 pin ICM7 or ICT7 housing, the catalog lists the IC-SP1-10 spacer. Examples include ICM7-26DAR with an Adams Rite cam, ICR7-26D and the Schlage large format ICSR26D. Our SFIC vs LFIC guide explains the two core formats.

What to note before you order

• Type: mortise, rim, thumbturn, dummy or IC housing
• Length, for a mortise cylinder
• Keyway and pin count of your key system
• The cam on the old cylinder
• Finish and keying

Browse all GMS products, mortise cylinders and rim cylinders on our store.

Not sure which GMS number replaces your cylinder? Our customer support team is available Monday - Friday, 8 AM - 4 PM Central Time, at 1-888-800-7789 or [email protected].