Originally Posted by absntr
What Mouton said - maybe $10 for an install depending on where you go. If you have the tools, you can do it yourself. Measure the spindle and go get the closest or appropriate length. Probably something in the 68x115 range if it's an older bike and you're using a double crank.
115 is a bit huge... I'd suggest 107-109.5 - you might improve your chainline is you were merely making do with what you originally had with the bike.
I've never even heard of a 115.