The tint iis dark and no one will be able to see through the envelope. However the adhesive on the closure is easy to reopen and close. That’s fine if you need to reopen it. But it will also make it easy for someone else should it fall into the wrong hands. So you may want to add strong tape if necessary.
I bought the security tinted envelop which was marked $1 more than the non security tinted envelop. I bought this on my way to drop off a check much to my surprise when I looked at the envelop in the light I could catch the writing On the check without straining which was really odd. Otherwise its like any other envelope with a self adhesive strip which is convenient. Just make sure you Put a blank paper to keep it secure from prying eyes.
I liked the other envelopes better. I only got these because you didn’t have the other ones. I prefer the others because I got more and were more secure. I couldn’t find them. I will have to find the others some other place. BAH HUMBUG! I do not recommend them.