An IP rating is the Ingress Protection code defined by the international standard IEC 60529. The first digit rates protection against solids such as dust, on a scale of 0 to 6, and the second digit rates protection against water, on a scale of 0 to 9. An X means that part was not rated. So IP67 is dust-tight and survives temporary immersion, IPX7 survives the same immersion but has no dust rating, and IPX8 survives continuous immersion beyond the IPX7 test, to a depth and time the manufacturer specifies.
The codes are precise, but they do not mean "more is better" in every direction. They also leave out several things shooters care about, such as fogging and what happens to an open emitter in the rain.
Key takeaways
- IP codes come from IEC 60529: the first digit covers solids (6 = dust-tight) and the second covers water (7 = temporary immersion, 8 = continuous immersion).
- An X is not a zero. It means that element was not rated, so IPX8 says nothing either way about dust.
- An IPX7 or IPX8 rating does not by itself cover water jets. A product has to be tested and marked for both, for example IPX6/IPX7.
- IPX8 has no fixed depth. The manufacturer sets the conditions, so check its figure if depth matters.
- Trijicon and EOTech often quote a depth instead of an IP code, such as 20 metres for the RMR Type 2 and 10 metres for the EXPS3.
How to read an IP code
IP stands for Ingress Protection. The code has two digits after the letters IP:
- First digit, solids: 0 (no protection) to 6 (no ingress of dust).
- Second digit, water: 0 (no protection) to 9 (high-pressure, high-temperature water jets).
Where a maker has only tested one of the two, the other is replaced with an X. Weapon lights and optics are often rated for water only, which is why you see IPX7 and IPX8 so often.
First digit: solids
| Digit | Meaning |
|---|---|
| 5 | Dust-protected: dust is not entirely kept out, but not enough gets in to affect operation |
| 6 | Dust-tight: no ingress of dust |
| X | Not rated for solids |
Second digit: water
| Digit | Meaning |
|---|---|
| 4 | Splashing water from any direction |
| 5 | Water jets from any direction |
| 6 | Powerful water jets |
| 7 | Temporary immersion, tested at 1 metre for 30 minutes |
| 8 | Continuous immersion, under conditions stated by the manufacturer that are more severe than the 7 test |
| 9 | High-pressure, high-temperature water jets |
| X | Not rated for water |
Up to 6, each water level includes the ones below it. Immersion (7 and 8) is a separate test. A sight rated only IPX7 has not been tested against jets, and one rated IPX6 has not been tested for immersion. Products that pass both are dual-marked, for example IPX6/IPX7.
The ratings you'll see on optics and lights
| Rating | What it means | Examples, per the manufacturer |
|---|---|---|
| IP67 | Dust-tight, and survives the 1 metre, 30-minute immersion test | Holosun HS507C X2 and HS510C; HM3X-Micro magnifier; Primary Arms SLx 1X MicroPrismT |
| IPX7 | Survives the same immersion test; no dust rating | SIG ROMEO5 Gen II and ROMEO1PRO; Streamlight TLR-1 HL |
| IPX8 | Continuous immersion beyond the IPX7 test, to the maker's stated conditions | Holosun EPS Carry and HE512T; SIG ROMEO8T and ROMEO4XT-PRO |
| IP68 | Dust-tight and continuous immersion | Holosun HS515CM and HS515GM (not stocked) |
Note that the HE512T is an open reflex sight with an IPX8 rating, while the enclosed HE509T X2 is rated IP67. An IP rating tells you how well the electronics are sealed, not whether the emitter is enclosed.
Makers that quote a depth instead
Several makers skip the IP code and state a depth from their own testing:
- Trijicon RMR Type 2: waterproof to 20 metres (66 ft), according to Trijicon's spec sheet.
- EOTech EXPS3 and XPS3: 10 metres (33 ft).
- EOTech XPS2: water-resistant to 3 metres (10 ft).
These figures are useful, but they are not IP codes and they are not directly comparable, because each maker sets its own test. The EOTech difference is worth knowing if you are choosing between the XPS2 and XPS3.
What actually matters in the field
Rain and open emitters
Any of the immersion ratings above will keep British rain out of the electronics. The weak point on an open reflex sight is different: a drop of water, mud or snow sitting on the emitter window can block or distort the dot, however well the body is sealed. That is a design question, not a sealing one, and it is the main argument for an enclosed sight. Our enclosed vs open red dot guide covers it, and the enclosed red dot range shows the options.
Fogging
IP codes do not cover internal fogging. That depends on whether the optic is purged and filled with a dry gas. Primary Arms lists its 1X MicroPrisms as nitrogen-purged, and Trijicon's RCR is described at launch as filled with argon to prevent fogging. Look for that line on the spec sheet as well as the IP code.
Weapon lights
Most weapon lights are rated for water only, typically IPX7. The switch, tailcap and battery compartment O-rings are the parts that wear, so check them after hard use and whenever you change batteries. Our Streamlight TLR comparison and weapon light range show the ratings model by model, and the lumens vs candela chart covers output.
Battery doors
A seal is only as good as its last battery change. Side-loading trays, such as those on Holosun's current sights, let you change the cell without removing the sight. Wipe the tray and seal before closing it, and do not overtighten the cap.
Expert tip
Do not jet-wash an optic or light rated only IPX7 or IPX8. Those ratings are for immersion, not for pressurised water. Rinse mud off gently under a tap and dry the lenses the way our optic and weapon light maintenance guide describes.
Frequently asked questions
Is IP68 better than IP67?
For immersion, yes: 8 means continuous immersion beyond the 7 test, to the maker's stated conditions. Both are dust-tight. Neither covers water jets unless the product is also marked 5 or 6.
How deep is IPX8?
The standard does not fix a depth. The manufacturer sets the conditions, which must be tougher than the IPX7 test, so look for the maker's own depth and time figure.
Is IPX7 enough for rain?
Yes. It is an immersion rating, well beyond what rain puts on an optic. What you notice in rain is water on the lens or emitter window, not water inside the sight.
Does IPX8 mean the sight is dust-proof?
No. The X means dust protection was not rated. Look for a 6 in the first position, as in IP67 or IP68, if dust matters.
Shop this guide
- Enclosed Red Dot Sights — sealed emitters for wet, muddy days
- Red Dot Sights — ratings listed on each product page
- Weapon Lights — IPX7 and better rifle and pistol lights
