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Conditional substitute

381 vs 391

Both are 11.6 × 2.05 mm silver oxide / zinc cells at 1.55 V nominal, but their drain designations differ (SW: low-drain profile versus W: higher-drain profile). Preserve the device-specified class.

Conditional substitute

Both are 11.6 × 2.05 mm silver oxide / zinc cells at 1.55 V nominal, but their drain designations differ (SW: low-drain profile versus W: higher-drain profile). Preserve the device-specified class.

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.
FieldSR1120SW / 381SR1120W / 391
Dimensions11.6 × 2.05 mm11.6 × 2.05 mm
Voltage1.55 V nominal1.55 V nominal
ChemistrySilver oxide / zincSilver oxide / zinc
DrainSW: low-drain profileW: higher-drain profile
RechargeableNo — primary cell; do not recharge.No — primary cell; do not recharge.

Direct answer

381/SR1120SW and 391/SR1120W share an 11.6 × 2.05 mm envelope and silver-oxide chemistry. Device guidance must resolve the remaining low-drain versus higher-drain choice.

Both are 11.6 mm in diameter; heights are 2.05 mm and 2.05 mm. Both are 11.6 × 2.05 mm silver oxide / zinc cells at 1.55 V nominal, but their drain designations differ (SW: low-drain profile versus W: higher-drain profile). Preserve the device-specified class.

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

Why these codes are confused

SR1120SW / 381 and SR1120W / 391 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.