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Same size, different electrical family

LR1120 / 191 vs SR1120SW / 381

The 11.6 × 2.05 mm envelope matches, but the electrical families do not: Alkaline manganese dioxide / zinc at 1.5 V nominal versus Silver oxide / zinc at 1.55 V nominal. Physical fit is not equivalence.

Same size, different electrical family

The 11.6 × 2.05 mm envelope matches, but the electrical families do not: Alkaline manganese dioxide / zinc at 1.5 V nominal versus Silver oxide / zinc at 1.55 V nominal. Physical fit is not equivalence.

Top profile · Ø 11.6 mm
Side profile · 2.05 mm high
Original proportional profiles. Scale is consistent within this diagram; screen size is not a physical ruler.
Top profile · Ø 11.6 mm
Side profile · 2.05 mm high
Original proportional profiles. Scale is consistent within this diagram; screen size is not a physical ruler.
FieldLR1120 / 191 / LR55SR1120SW / 381
Dimensions11.6 × 2.05 mm11.6 × 2.05 mm
Voltage1.5 V nominal1.55 V nominal
ChemistryAlkaline manganese dioxide / zincSilver oxide / zinc
DrainElectronic applications including short high-rate pulsesSW: low-drain profile
RechargeableNo — primary cell; do not recharge.No — primary cell; do not recharge.

Direct answer

LR1120/191 and SR1120SW/381 both measure 11.6 × 2.05 mm. LR1120 is 1.5 V alkaline, while 381 is 1.55 V silver oxide with an SW low-drain designation. They are same-size electrical alternatives, not exact equivalents.

Both are 11.6 mm in diameter; heights are 2.05 mm and 2.05 mm. The 11.6 × 2.05 mm envelope matches, but the electrical families do not: Alkaline manganese dioxide / zinc at 1.5 V nominal versus Silver oxide / zinc at 1.55 V nominal. Physical fit is not equivalence.

Do not infer acceptability from fit alone. The device maker’s complete code and current instructions remain authoritative.

Why these codes are confused

LR1120 / 191 / LR55 and SR1120SW / 381 share part of their dimensions, naming pattern or retail context. The table separates the four fields that a one-line cross-reference can hide.

When the alternative may be acceptable

Only when the device or battery manufacturer explicitly permits the alternative after accounting for size, nominal voltage, chemistry and drain behaviour. Otherwise use the specified family. Never stack cells or modify a compartment to compensate for a height difference.