Ive had my sentinels about a year and have known  that the left tube's ocular lens has to be set at -3 while the right tube is set at 0.  I just thought it was my eyes but i just noticed that the whole left  back piece isnt screwed onto the housing as far as the right side.  Neither side is loose and i cant move thm.  Is this normal?  Picture attached

The outer part of the ocular assembly moves in and out, and so does the center lens cell assy, so they can be offset and still produce the same outcome. The diopter numbers could match too (but adjustment range might not).

Collimation is adjusted by rotating the whole eyepiece, meaning the outer part of it which rotates the lens cell with it, and so if you screwed either of the eyepieces in/out you'd lose collimation unless you mark the position and screw in/out in full 360deg increments/decrements.

I think im following but just to be sure, my left tube(right side of picture above) has the threads on the tube housing showing. Like the whole eye piece wasnt tightened down far enough.  Are you saying thats ok?  It may be, it just semed weird that one ocular lens is cranked in while the other is cranked out to achieve focus.  Thanks for the reply

The eyepiece consists basically of two different pieces. The outer part, that is the one that screws onto the housing, and the inner part that has all the lenses, which then is threaded inside the outer part.

Both move in & out independently, but the lens cell rotates with the outer part.

If you move the outer part toward the tube, then you just need to screw the lens cell outward. Adjusting diopter moves the lens cell in & out. Only thing that matters on the image clarity & focus is the distance of the lens cell from the tube. It is one piece that has no moving parts, it is only threaded inside of the outer part and when rotated (diopter adjustment) it moves inside the outer part.

The only issue with having them offset from each other that much is the difference in range of usable diopter settings on each side. If you can achieve good focus on both sides, then in practice it doesn't make a difference. You can see that while the outer part of the eyepieces are offset compared to each other, but the inner part, the slimmer portion that peaks out from the rear, are on the same level. The lenses are the same distance from the tube anyway (when you have good focus and assuming your eyes have the same need / lack of correction)

Thanks.  I understand now.  I wonder why TNVC shipped them this way?  They do work fine, however

That's a good question. Perhaps TNVC will spot this thread and come back, but that is a rather usual sight to see while based all that I know is not necessary for any reason. For collimating binos you need to offset them slightly, but that is only +- half a turn (of the outer part, the threads are fine so very small offset) per side, totaling one full turn.

I understand it's easy to just slap them on and be good with it, but doesn't take that long to make them look nice too by not being offset that much.

Tagged as am looking into binos soon and this is my  go to brand

You wont be disappointed.  ive been very happy with mine.  I shot with them at least once a week from last fall to spring, until the time changed.  i will be back out with them again when the time changes and it starts to get dark early.  i never paid attention to what the ocular lens was set on, just focused them and went on.  they work flawless. i just noticed that they're not set up identical and wondered why.

And if for some reason that would bother you, it's simply a matter of loosening the slim lock ring and then screw in/out either of them by exact 360deg full rotation increments (so that collimation is retained, that one is harder to get adjusted without the test equipment)