My iphone 4s makes the best pics so its no camera question but...
Will these 2 fit on each other?
Snap on Front Cap For 67mm Canon Nikon Sony Pentax Lens | eBay
Hoya HMC Super UV(0) Multi-Coated 67 mm Filter | eBay

I want to glue that glass to my projector as laser aperture.
Then want that cap thing to functio. As protection when not in use.
Does it really snap on and fit?
Or do i need another cap or a whole other solution?

Yes, the cap will fit into the filter nicely. I say this because I own a Nikon DSLR and have gone through many lens caps and filters.

It won't "snap" on but you'll need to squeeze the two sides to place it onto the filter.
It's a spring mechanism, so you'll need to squeeze the sides to detach it as well.

However, two problems I may see with this:
1. Hopefully there isn't a lot of reflection back into the projector or it might get damaged. But since it's multi AR coated, it should be fine.

2. How big is your projector aperture? Good quality filters do get pricey as the diameter goes up, so you might want to find a smaller one to save a bit of $$.

If reflections are a concern, the best camera filters are from B+W Schneider, but they are very expensive.

Good luck!

Thanks, but the one i i linked were personally recommended by alot of guys

Yup, the Hoya filter isn't bad at all-- it's one of the best MCUV filters.

How big is the aperture? If you want the absolute quality filter, you could reduce the filter diameter so the price won't be so high and get a B+W filter.

Let me know how it works out!
Cheers.

Thanks, but the point is that i want to protect that glass...
So thats why i want to know if i such a item i linked fits.

Haha, simple answer then: yup, it will fit fine.

Good luck!

thanks will keep you up to date how it works out

btw, 100% awesome avatar

You're welcome.

Thanks, love the OMG cat.
Spent a bit of time searching for a perfect GIF for this forum.

Cheers!