Running out of battery in the field is avoidable — if you know which cell your optic takes and carry a spare. Most red dots run for years on a single coin cell, but the exact type varies by model. This chart covers the popular optics we stock. Always confirm against your optic's manual, as makers occasionally revise designs.
Battery by optic
| Optic | Battery |
| Holosun 507C / 407C (X2 & X3) | CR1632 |
| Holosun 507K / 407K (X2) | CR1632 |
| Holosun EPS / EPS Carry / RONIN EPS Carry | CR1620 |
| Holosun HE508T X2 | CR1632 |
| Holosun HE509T / HS509T X2 | CR1632 |
| Holosun AEMS PRO X2 | CR2032 |
| Holosun AEMS EVO Dual | CR123A |
| Holosun HS510C | CR2032 |
| Holosun SCS (solar) | Solar — no user-replaceable cell |
| Trijicon RMR Type 2 / SRO | CR2032 |
| Trijicon RMR HD | CR2032 |
| Trijicon MRO / MRO HD | CR2032 |
| SIG ROMEO5 Gen II | CR2032 |
| SIG ROMEO5XDR Gen II | AAA |
| SIG ROMEO8T-AMR | CR123 |
Don't confuse the coin cells
CR2032, CR1632 and CR1620 look similar but differ in thickness and capacity — the last two digits are the height in tenths of a millimetre (a 2032 is 3.2mm thick, a 1620 is 2.0mm). They are not interchangeable, so match the exact code.
Get the most from a battery
- Use the manufacturer's specified cell — a quality CR-grade lithium lasts longest.
- Optics with Shake Awake or motion activation sleep when idle, stretching life to years.
- Solar Failsafe models top up in daylight, reducing drain.
- Note your install date and swap annually for carry/duty optics regardless of charge.
Shop optics & spares
Browse red dot sights, pistol dot sights and the Holosun, Trijicon and SIG Sauer ranges. New to Holosun model numbers? See our Holosun buyer's guide.
Frequently asked questions
What battery does the Holosun 507C use?
A CR1632 coin cell (507C X2 and X3). The smaller 507K/407K also use CR1632; the EPS Carry uses CR1620.
What battery does the Trijicon RMR use?
The RMR Type 2 and SRO use a CR2032.
Can I use a CR2032 instead of a CR1632?
No — they're different thicknesses and won't fit/seat correctly. Always match the exact code.
UK Delivery & Support
Every optic is UK-stocked and dispatched tracked from our UK warehouse — no import duties or customs delays — with UK-based support.