Interchangeable Cores: SFIC vs LFIC and How to Read Core and Cylinder Numbers

Before you order an interchangeable core, or a lock that takes one, check the format. The core has to match its housing. An interchangeable core is the keyed part of a cylinder that can be taken out of its housing with a control key. The sections below cover small format (SFIC) and large format (LFIC) cores as BEST, Schlage and Sargent define them, what is ordered separately, and how to read core numbers such as 1C7A2, 6300 LA 15 or 23-030.

SFIC and LFIC: what the manufacturers mean

SFIC stands for small format interchangeable core. BEST says it invented the SFIC in 1921, and its Standard cores are made as 6-pin and 7-pin SFIC. Schlage's price book labels SFIC "BEST Style" and lists uncombinated SFIC cores for BEST keyways. Sargent lists its own SFIC cores as 7300B (6-pin) and 7P-7300B (7-pin).

LFIC stands for large format interchangeable core. Sargent's conventional large format core is the 6300 (6 pins). Schlage calls its own core FSIC, full size interchangeable core (standard catalog number 23-030), and Sargent's catalog calls the Schlage core a Schlage 6-pin LFIC.

Core, housing and control key

The core goes into a housing: a mortise cylinder, a rim cylinder or a lock prepared for a core. Schlage's interchangeable core mortise cylinder instructions show the core being installed and removed with the control key. The documents treat the three parts as separate items:

• The core. Sargent's catalog specifies a core ordered separately by model number, keyway and finish, for example 6300 x LA x 15, and says its cores come with 2 nickel silver keys.
• The housing or lock. For its mortise and rim cylinders, BEST asks for the keymark and number of keys, or L/C for less core. In Schlage's ND Series, J means less FSIC and B means less SFIC. In Sargent's 10X Line, 60- is a lock that accepts an LFIC and comes with a disposable plastic core, with the permanent core ordered separately; 70- is the same for SFIC.
• The control key. On its ND Series and CL Series pages, Schlage's price book says control keys are not furnished with the locks and are ordered separately.

Construction cores are temporary and separate too. Sargent's 64- and 72- options supply a keyed construction core, with the permanent core ordered separately. Schlage's construction cores come with no keys and need a separately ordered control key to be installed and removed.

Matching the core to its housing

BEST describes its 1E mortise cylinders as featuring the BEST interchangeable core. In its 1E Series how-to-order, the 7 stands for a 7-pin housing that accepts all BEST cores. BEST also states that its Cormax cores are compatible with all existing BEST interchangeable core housings.

Large format cores are listed brand by brand. In Sargent's 10X Line catalog, one lever option covers 6-pin and 7-pin SFIC, but the large format cores of Schlage, ASSA ABLOY Accentra and Medeco each have their own: SF- for Schlage 6-pin LFIC, YRC- and YRC-7P- for ASSA ABLOY Accentra 6-pin and 7-pin LFIC, and MRC- for Medeco 32 Series 6-pin LFIC. Schlage's ND Series lists separate less LFIC options for Medeco, Corbin Russwin, Sargent and Yale.

The core type matters even within one brand: Sargent notes that standard cores and XC cores require different tailpieces, so the lock option must match the permanent core. Before ordering a core for an existing door, check the brand and format of the housing and the keyway of your key system.

How to read a core part number

BEST 1C cores (SFIC)

BEST's how-to-order for its C Series cores reads 1C 7 A 1 606:

• Core type: 1C standard or 1CP premium, among others.
• Core size: 7 pins, or 6 pins for 1C only.
• Keyway code: the keyway, such as A or E.
• Combination code: 1 uncombinated, 2 combinated.
• Options, such as K for key trap, then the finish, such as 606 or 626.

So Best 1C7A2626 is a standard 7-pin core in the A keyway, combinated, in 626 finish, and 1C7A1-626 is the same core uncombinated.

Sargent LFIC cores (6300)

6300LA15 reads 6300 (large format core, 6 pins) x LA keyway x 15 finish, which Sargent lists as satin nickel. Sargent's 10X Line catalog lists its large format cores in 04, 15 or BSP finish.

Schlage FSIC and SFIC cores

Schlage orders cores as catalog number . finish . keyway . keying: 23-030 . 626 . S123 . KD for a standard FSIC keyed different, or 80-037 . 626 . R125 . MK for a combinated 7-pin SFIC, master keyed. Schlage 23030D123626 is the 23-030 core in the D123 keyway and 626 finish. The price book lists D123 as an Everest D keyway, and all Everest D keyways are restricted.

Combinated or uncombinated

Schlage's SFIC core table notes that uncombinated cores are furnished less keys, pins and springs, and Sargent's 10X catalog lists its uncombinated SFIC option as packed loose. A combinated core is ordered with its keying: BEST asks for the keymark and number of keys, and Schlage's 80-037 example ends in MK.

Interchangeable cores and housings on our store

These titles start with the brand and manufacturer's number, followed by words for its parts, such as format, pins, keyway, combinated or uncombinated, and finish:

• Best 1C7A2626 7-Pin A Keyway Combinated Core
• Best 1C7A1-626 7 Pin A Keyway Uncombinated Core
• Best 1E74C4RP3626 7-Pin Mortise Cylinder Housing: 1E series, 7-pin housing, 4 standard mortise, C4 standard cam, RP3 7-pin mortise rings, 626
• Sargent 6300LA15 LFIC Core: LA keyway, satin nickel
• Schlage 23030D123626 Full Size Interchangeable Core
• Schlage ND50BSPA626 (B, less SFIC) and Schlage ND50JRHO626 (J, less FSIC)
• Sargent 60-10XG37 LB 26D: the 60- prefix for a lock that accepts an LFIC

Browse interchangeable cores and housings, cylinders and cores and mortise cylinders, or the brand pages for BEST, Sargent and Schlage. Finish numbers such as 626 are explained in our finish codes chart, and the ND50 and 10XG37 functions in lock functions explained.

Ordering a core for an existing key system or a restricted keyway? Our customer support team is available Monday - Friday, 8 AM - 4 PM Central Time, at 1-888-800-7789 or [email protected].