Kwik-Klip (continued)
Summary -
1. The Kwik-Klip (as it says on their site and the Cabela's ad) only fits long action calibers, such as the .30-06 and .270. The .308 is a short action caliber.
2. The Kwik-Klip, as you can see from the pictures, is a replacement trigger guard and bottom metal, which then accepts their proprietary magazines. Looks like a short (flush mount) and a longer 10 rd magazine are available.
3. This doesn't fit all Remington 700's without some modification. The 700 SPS may work fine, as it has no large stock notches for a detachable magazine. The 700 SPS DM may also work after replacing its bottom metal, but the stock will have to have those "notches" filled in with something. Probably unsightly. (In other words, if you are going to install a Kwik-Klip, the DM model doesn't seem to get you anything except a worse fit...)
So, as another reply said earlier, as you want
.308
10 round detachable magazine
cheap (< $800)
you can have any two of these. If you want all three, the closest is the Kwik-Klip in a caliber similar to .308, the .30-06.