Opticron Rubber Objective Lens Covers 50mm OG S Pair fits models with Outer Diameter 56~58mm...

I bought these for my Swarovski Curio 7x21 compact pocket binocular which I will return due to jittery image in hands see my review on ZeeBooth on this binocular. These objective covers however are very nice and fit these binoculars very well. Not too tight but they work excellent and protect the objective lenses. Give these a try if you own a Curio 7x21 binocular.

Leupold Yosemite 8x30 binoculars: measured objective OD was 43mm (old binoculars but I still use them a lot). These 42-44mm covers are a perfect fit. Snug but easy to slip on. Good quality material. These binoculars came with caps that have no attachment, so this was a "must" (wish I had done this long ago). I was taken back by the price, but once I received these covers, it appears they might be worth it. Attached pic shows one side with cap on and the other side with cap removed so you can see the natural fall point. Nikon Laserforce 10x42 range-finding binoculars: measured objective was about 54.6. The 53-55mm covers were a perfect fit. I was a little worried that they'd be too snug, but not the case. They fit just as nice as the aforementioned covers described above. The covers that come with these Nikon binocs are 'plug-inside the objective tube' rather than a cover. After several uses, I found that much as I like the plug design for sealing out the elements, they just never went in easy. It always took a little fiddling and some moderate pressure to get them in (one slip and you could easily end up with your greasy fingerprint smushed onto the lens). These new covers go on very easy without any fiddling or unnecessary force, and they are plenty snug that they won't come off. If I had not purchased these covers for my Leupold binocs, I would never have purchased for covers my nice, new, and expensive Nikon binocs. But I'm glad that I did. Much as I like these Nikon range-finding binoculars (they are awesome), I was getting tired of spending 30 seconds and, arguably more importantly, having to divert all of my attention to the binoculars just to secure the objective lenses.