I bought a pack of them a few weeks ago. They are very easy to install and work great. I went back to buy six more and it took me about 2 weeks to find them in any store. I know you can buy them from cabelas for $14.99 but I waited and found them for $10 so I bought two more packages. I would highly recommend them. Also they did make my groups a little tighter at 20yrds.