I lost the lens cap of my
Nikon AF-S 24-70mm/2.8G ED in a cave. Rather than relying on the lens hood, I was foolishly trying to replace the cap onto the lens, when, knocked out of my hand, it went rattling into an underground stream and is now doubtless part of the future archaeology of the site. Fortunately I had a spare with me, purloined from another lens a few days before. As soon as we got back, I ordered one of these, which was delivered efficiently the next day.
This cap has three basic characteristics:
* robust
* spring-clip type
* Nikon logo on the front
You may or may not want the Nikon logo on the front, though if you ever intend to resell the lens, this will affect the value. I do have an unbranded cap on one of my lenses, but, given the choice, I'm happy enough to keep the Nikon branding going.
The spring-clip construction, in my opinion, is much better than other types. Spring-clip is much better than push on if the springs are strong enough, and, over the course of ten years with Nikon and more lenses than years, I've never found any of the springs to become soft.
Finally, the design of the cap gives it more protection against shocks from the front than the simple flat plastic types which off-brand replacements often are.
This is a 77mm cap, which means it goes on lenses like the 70-200 f/2.8, the 80-200 f/2.8 and the 24-70 f/2.8. These are expensive lenses. Unless there is a particular reason why you don't want people to know you are shooting Nikon (for example, to limit the chances of theft -- a little), then replacing a lost Nikon cap with this makes far more sense than trying to save a couple of quid. And, if you're going anywhere where the lens is in danger and the cap is as well, it may just be worth your while to carry a spare.