Once I started using them, it about doubled the life between string jobs for me. If you are paying a lot for stringing, that could save you a fair amount of money if you tend to go through strings quickly. It also keeps the strings from moving around each time you strike the ball, creating a more consistent string pattern.You should be able to find them in a good sporting goods store or 'pro shop'. Seems to me they are about $4-$5/ pack. Personally, I prefer the Babolat Elastro Cross II brand but there are other brands on the market. If not, you can order them from www.tenniswarehouse.com
. Don't bother to pay your stringer to put them in unless you want to observe the pattern that he puts in. They're easy to use and you can do it yourself while you watch a match on TV. Some people feel that string savers increase the tenssion by a pound or two when they are put in so they will lower their string weight a pound or two when they string so they will back off on the string tennsion a pound or two. Personally, I like a stiff racquet but that's me and you would have to try them and see how you feel.
Another thing I do is I have all my racquets strung the same, and at the same time. Then I rotate them by sets, the goal is to have them play similar and wear as long as possible as a group.
(Sigh) Tennis players are as finickey about their equipment as golfers and surfers are about their 'sticks'.
I hope some of this made some sense.