What is Light Center Length? (LCL)

The distance between the center of the filament, or arc tube, and a reference plane - usually the bottom of the lamp base. Refer to the following chart for reference plane locations.

Base type L.C.L Reference Plane Location
All screw bases (except Mini-Can) Bottom of base contact
Mini-Can Where diameter of ceramic base insulator is .531 inches
3-Contact Medium Bottom of base contact
Mogul Medium Prefocus Top of base fins
Mogul Prefocus Top of base fins
Medium BiPost Base end of bulb (Glass lamps)
Bottom of ceramic base (Quartz lamps)
Mogul BiPost Shoulder of posts (Glass lamps)
Bottom of ceramic base (Quartz lamps)
2-Pin Prefocus Bottom of ceramic base
S.C. or D.C. Bayonet Candelabra Top of base pins
Medium Bayonet Top of base pins
S.C. or D.C. Prefocus Plane of locating bases on prefocus collar
Medium 2-Pin Bottom of metal base shell

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