- Cheap, they work, and last long.
... I use them in my spec ops reflex and my friend uses one in his scope. To give you an idea of how long the battery lasts, it's a 3 volt. An AA is 1.5 volts. These last me about 5 battles before they die. They look a little odd, round and flat like a penny (in case they still haven't put the picture up yet). You may think your battery is defective but it fits right once you move it a bit. Where i get them they're $5, while the total here is only 1.09 counting shipping(not the base charge).
As i said in the title, they're cheap, they work and last long. I suggest you buy in bulk so you don't have to pay repeated base shipping charges.
I haven't used this specific one, they say it's for the spec ops reflex sight, but about a month ago they sent me an e-mail because i forgot the type, they said it was CR2025, and this is a CR2032, i don't really know the difference.