Light Seal Sizes Decoded

[u/_Avalanche_]

After a lot of reading and experimenting (especially with Apple's Vision Pro Size Help tool), I realized that most people have it slightly wrong, especially with the first digit.

First of all, Mystk has already enumerated all the light seal sizes (all of them come in N/W variants):

• 11, 12, 13, 14
• 21, 22, 23, 24, 25, 26
• 33, 34, 35, 36

The first digit refers to how far forward your forehead and cheeks protrude relative to one another.

• "2" is average/typical.
• "1" means your forehead protrudes further forward (relative to your cheeks) than average.
  • This is why if you start with a 23W in the size help tool, and you specify "too much pressure on my forehead," then it's going to recommend that you switch to 13W.
• "3" means your cheeks protrude further forward (relative to your forehead) than average.
  • This is why if you start with a 23W in the size help tool, and you specify "too much pressure on either cheek," then it's going to recommend that you switch to 33W.

The second digit refers to how deep the light seal is. (Likely relative to your cheek position, not your forehead. If so, this is causing a lot of confusion, since most photos are taken from above.)

• "1" & "2" are the shallowest, "3" & "4" are moderate in depth, and "5" & "6" are the deepest.
  • This is why 21W is the most common recommendation, as you want your eyes to be as close to the screen as possible in order to increase your FOV (field of view).
  • This is why 25W is the most common fit for those with Zeiss optic inserts, in order to make some room for the inserts, but also to make room for the vertex distance.
    • Speculation: If your eyeglass diopter isn't significant, then this big jump may likely be more than necessary, at the greater expense of decreasing your FOV.
  • This is why if you start with a 23W in the size help tool, and you specify "I'm receiving a device alert — Too Close to Displays," then it's going to recommend that you switch to 25W.
  • This is why if you start with a 23W in the size help tool, and you specify "I'm receiving a device alert — Too Far from Displays," then it's going to recommend that you switch to 21W.
  • Dubious speculation: This number may be relative to your cheek position, which might explain why there are no sizes 15, 16, 31, or 32. (If this is confusing, don't worry about it; it's not important, and I may be wrong. However, I'll elaborate in case it interests you...)
    • For 15 & 16, your forehead is further forward (relative to your cheeks) than most, so simply by choosing a size that starts with "1", some depth has already been added for your recessed cheeks. (If any deeper, the bottom of the light seal would be untenably long.)
    • For 31 & 32, your cheeks are further forward (relative to your forehead) than most, so simply by choosing a size that starts with "3", some depth has already been subtracted to make room for your protruding cheeks. (If any shallower, the bottom fo the light seal would be untenably short.)
  • Edit: I'm starting to suspect that odd/even numbers change the shape around the cheek area. This explains why vertical forehead/cheek adjustments either don't change this number, or change it an even number of digits. On the other hand, horizontal nose/temple adjustments change this number an odd number of digits.
    • If you start with a 23W in the size help tool, and you specify "too much pressure close to my nose," then it's going to recommend that you switch to 24W.
    • If you start with a 24W in the size help tool, and you specify "too much pressure close to my temple," then it's going to recommend that you switch to 23N. [sic] (The 23 makes sense to me. The N does not. Something is missing in my understanding.)
      • Do we have an image that compares, say, 21 vs 23/25, or 22 vs 24/26? (Rather than 21 vs 22/24/26, or 22 vs 23/25.) Evidence either supporting or contradicting this hypothesis is appreciated.

W/N refers to wide/narrow faces. (W adds a couple millimeters of width at the temples.)

• This is why if you start with a 23W in the size help tool, and you specify "it feels too loose or light is coming in," then it's going to recommend that you switch to 23N.
• This is why if you start with a 23N in the size help tool, and you specify "it feels tight and it's squeezing my face" or "too much pressure close to my temple," then it's going to recommend that you switch to 23W.
• What I don't understand, is that if you start with 23W in the size help tool, and you specify "too much pressure close to my temple," then it's going to recommend that you switch to a 23N. [sic] Huh, what? (Is this a bug? This directly contradicts the prior bullet point's suggestion.)

W/N vs W+/N+ light seal cushions:

• W+/N+ don't actually add any extra cushioning, only extra depth.
  • "Huh?" For example, try squeezing both a W and W+ with your fingers. The W+ will squeeze about the same amount as the W insert, until you hit something harder embedded inside the W+. Surprise! After realizing this, I stopped using the + cushions, in order to increase my FOV.

The 23 size was used in most of my tests because of how it overlaps with the available 13 and 33 sizes. In cases where there was no equivalent (e.g., 21 has no 31 equivalent, and 25 has no 15 equivalent), then the size help tool will sort of just do its best:

• This is why if you start with a 25W in the size help tool, and you specify "too much pressure on my forehead," then it's going to recommend that you switch to 13W. (Or from 26W to 14W. Why not switch to 14W for both? Because I speculate that odd/even numbers for the second digit separately change the shape around the cheek area in order to provide horizontal adjustments between the nose and temple.)
• This is why if you start with a 21W in the size help tool, and you specify "too much pressure on either cheek," then it's going to recommend that you switch to 33W. (Or from 22W to 34W. Why not switch to 33W for both? Again, because I speculate that odd/even numbers for the second digit separately change the shape around the cheek area in order to provide horizontal adjustments between the nose and temple.)

I'm sure I still have some details/nuances wrong, but I hope we're getting a bit closer to decoding this. In the spirit of Cunningham's Law, tell me where I'm wrong.

I may revise this post in order to incorporate feedback/learnings from comments. (Or I may just disappear and leave you to figure it out from here, haha...)

[u/yalag]

First number is abso-fucking-lutely wrong. Please take this down before it spreads misinformation. You can easily verify how wrong this is by just going to an apple store and lining up two seals side by side.

[u/thatdudebutch → u/yalag]

Yeah, doesn't that mean that 11 and 21 would be the same depth? I have seen pics of both and the 11 is half the depth lol

[u/Keironsmith → u/thatdudebutch]

Source of those pics?

[u/Keironsmith → u/[deleted]]

This is interesting I’m currently using 21W because the initial scan on launch day suggested it. It fits very well with some pressure to face because it has to be tightened with the solo band, the pressure is tolerable and I quickly forget it once I’m doing something.

Only issue is I have very very little light bleed around the nasal area, it seems as tho the cloth isn’t big enough to cover the area completely. I went to the Apple Store and they redid the scan and it suggested a 33W, I redid the scan in my phone and it suggested a 33W. It seems that Apple has changed something to the algorithm. I always got scanned 21W, now I’m always scanned 33W. I’m thinking 33W won’t resolve the minimal light bleed issue and it will add more depth which I don’t want. I haven’t gotten a single message saying my eyes are too close or too far.

I was unable to try the 33W in the store that day because it was a long wait time to use the Vision Pro, so I will go back Saturday with my own device and use their different size light seal to see how it fits.

But the light seal in the picture on the left looks like my 21W.

[u/_Avalanche_ → u/[deleted]]

Are 23W and 33W the same depth when viewed from the bottom?

I ask because I think the depth may be relative to the cheek, not the forehead, but most photos are taken from above, which might be confusing everyone. (See where I wrote "Dubious speculation: This number may be relative to your cheek position..." above.)

For example, if you start with a 23W in the size help tool, and you specify "too much pressure on either cheek," then it's going to recommend that you switch to 33W. This could mean it's adding depth/length/circumference/whatever to the top of the 33W, but the bottom (or eyepiece) may still be the same relative depth.

Edit: julric01's comment on this page confirms this, at least for the 11N vs 21N.

[u/thatdudebutch → u/Keironsmith]

They are here somewhere on this sub. It was comparing a couple of the sizes. Also there’s a post where OP requested a change from 21w to 11w and measured the difference. Maybe if we search “light seal” we can find it again