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Conditional substitute

395 vs 399

Both are 9.5 × 2.7 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 9.5 × 2.7 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 9.5 mm
Side profile · 2.7 mm high
Original proportional profiles. Scale is consistent within this diagram; screen size is not a physical ruler.
Top profile · Ø 9.5 mm
Side profile · 2.7 mm high
Original proportional profiles. Scale is consistent within this diagram; screen size is not a physical ruler.
FieldSR927SW / 395SR927W / 399
Dimensions9.5 × 2.7 mm9.5 × 2.7 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

395/SR927SW and 399/SR927W share a 9.5 × 2.7 mm envelope. The choice is not a fit question; it is the low-drain SW versus higher-drain W requirement.

Both are 9.5 mm in diameter; heights are 2.7 mm and 2.7 mm. Both are 9.5 × 2.7 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

SR927SW / 395 and SR927W / 399 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.