O-rings for APLOS AP150 Dive Light

[VOGH]

I recently bought an APLOS AP150 dive light. Inexpensive, small, but very strong light (flood/wide angle) for 90 minutes or more. I like the magnetic rotary switch which allows you to select what you want without pressing a button until you find what you want. Chinese product, but certainly without prejudice a competitive product.
They enclosed two spare O-rings for the double sealing of the battery compartment. Unfortunately, these O-rings are rather thin, delicate. I measured something like 26 x 1,3 (in mm), maybe a tiny bit more or less. I suspect they will not last very long and I should have more than just a single set of spare parts. Asked for the spec of the O-ring the producer (Aplos) did not respond. And Amazon (or rather a Chinese company via Amazon) sold the light, but there is no way to buy or order O-rings. Does somebody happen to know the spec of the O-rings?
New insight July 12, 2025: Just in case someone else is looking for such O-rings. I just happened to find a standard O-ring for industrial and other purposes, 26 x 1.3, NBR 70, which is DVGW ‑ EN549 certified and apparently used in thousands of pieces, 0,1 € per piece. So this sounds very reasonable apart from the fact that you have to buy at least 122 pieces, O-Ring 26x1.3 - NBR - Nitrile - 70 Shore A - Black - ORS129520 Online Shop - Worldwide shipping . Maybe I just ask my sanitation installer.

 

[Mobulai]

26 x 1,3 (in mm)

Was the 26 inner or outer diameter? Might help at better identification of a standard size (cheaper)

I found this extremely overpriced one O-ring 26x1.3 - FFKM - FFPM - 75 Shore A - Black - Kalrez® 6375 - ORS58611 (Equivilent) Online Shop - Worldwide shipping

 

[VOGH]

Was the 26 inner or outer diameter? Might help at better identification of a standard size (cheaper)

I found this extremely overpriced one O-ring 26x1.3 - FFKM - FFPM - 75 Shore A - Black - Kalrez® 6375 - ORS58611 (Equivilent) Online Shop - Worldwide shipping

Thank you. 26 inner diameter. But I am still not sure about 26 nor 1.3. And I know these shops with extreme prices. I usually buy somewhere else. Nevertheless, it is expensive to try just to learn that you are only close to the right size.

 

[Mobulai]

For metric (nominal) orings there’s a 26 x 1 or 1.5
I’d go with the 1.5 (and lower shore nr — even if it means the oring dies sooner) to make sure it seals

You might have better luck measuring the groove diameter on the barrel of the light itself (for the 26)
For the CS I try to align a few passes inside the caliper jaws to get a better average of the measurement (and account for compression tolerances); the bigger the oring the more pass-throughs you can get

 

[VOGH]

For metric (nominal) orings there’s a 26 x 1 or 1.5
I’d go with the 1.5 (and lower shore nr — even if it means the oring dies sooner) to make sure it seals

You might have better luck measuring the groove diameter on the barrel of the light itself (for the 26)
For the CS I try to align a few passes inside the caliper jaws to get a better average of the measurement (and account for compression tolerances); the bigger the oring the more pass-throughs you can get

Thank you once more. A good discussion, helpful. Seems to converge.
Yes, I might give 26 x 1.5 a try. The seal is just the smooth end of the cap which slides over the O-rings when the cap is screwed on the body of the torch. Either it works with 1.5 (and low shore - actually I do not know the shore value of the original spares) or it cuts-off a little bit and/or squeezes the O-rings so much that I possibly could realize the damage and look for a different size.
On the other hand I have other new O-rings with 1.5 and they are obviously thicker than the ones of the torch. At the same time it is obvious that the spares are thicker than 1.0.
The smooth inside of the cap seems to be 31.2, the outside of the O-rings mounted on the torch seems to be 31.3. The groove for the O-rings seems to be 30. This seems to be consistent, but maybe I simply measure what I expect.
To confirm the 26 I compared a 26 x 2, which I have for different purposes, with the spares. And the inner diameter is very, very similar.
To add some confusion: with a magnifying glass I can easily see a slight seam on the O-rings, as expected.
To summarize: I shall try 26 x 1.5, check which shore values are available and check whether something between 1.2 and 1.4 is available at a reasonable price and a reasonable minimum order quantity.
And thank you again, your comments were appreciated!

 

[Mobulai]

On the other hand I have other new O-rings with 1.5 and they are obviously thicker than the ones of the torch.

Might be the constant compression and torsion ate at the old ones
And if you go for a very low shore (say silicone 50 instead of 60-70) hopefully they’ll compress enough to fit

Seems you already have a working method forward towards solution

slight seam

That’s the “flash”, the more of it you have the lower the quality of manufacturing

Glad I could help in any way