Short answer
Match the empty pack colour tab and the size printed on the aid or blister — size 10 (yellow) is not size 312 (brown).
IEC labels: ZA10 / PR70 for size 10; ZA312 / PR41 for size 312.
What is the same
Both are zinc-air primary cells used in many non-rechargeable hearing aids, activated when the tab is removed. Approximate height is about 3.6 mm for both.
What is different
Diameter: size 10 ≈ 5.8 mm; size 312 ≈ 7.9 mm. The wrong diameter will not seat in the battery door.
Runtime and which aids name each size differ — always follow the manufacturer’s non-rechargeable size table for that model.
Also not the same
Size 13 (orange / ZA13) is taller (~5.4 mm) than both 10 and 312 — see ZA312 vs ZA13.
Size 675 (blue) and rare size 5 are different again — see the hearing-aid size hub under Tools.
Do not use list
Do not swap size 10 and 312 by looking at height alone.
Do not use these cells in sealed rechargeable hearing aids — that is a different power system.
This is a size guide, not clinical fitting advice.