Customers most agreed on the following attributes:
I bought this lens cap to replace my Canon lens cap. I like to use this on because I can take the cap off and put it on while my lens hood is in place (there's a big hood on the 24-70 F2.8L) The canon design has smaller areas to grip and no grip in the middle, so is much harder to use while a lens hood is on. I guess the Nikon cap is also good, but I'd get shot if I had the Nikon on my Canon.
Using this on a Canon 17-55 lens. Much easier to attach and remove with the lens hood on than the stock lens cap. I have a 'standard' B+W UV filter on my lens and this lens cap attaches to it well. Does not slip off, etc.
I have several of these caps in different sizes. They perform there function perfectly. I especially like the ability to squeeze the center to apply or remove the cap. This makes them easy to use with lens hoods.
It's amazing that the rest of the lens manufacturers have not adapted this style. These lens caps solve a problem that most photographers have encountered. Trying to put the lens cap back on with the hood in place is nearly impossible if not awkward. When I bought a Tamron lens I thought this was the greatest thing ever. I bought these caps for all of my Canon lenses.
The Tamron snap in lens caps are, IMO, the best lens caps ever. When I got my first Tamron lens that came with this style cap, I immediately fell in love with it. You can easily insert or remove the cap with the lens hood in place. Also, the springs are strong and hold the cap very securely. I have upgraded all my lenses with Tamron caps.
These caps are great! Easy to grip and they allow you to remove/install the cap with a hood in place. I have replaced all of my Canon lens caps with these.