Four years, between $18.25 and $19 million. This is a good deal for the Bucs. I've written about it here and here, and I was pretty close to guessing the financial terms correctly both times, so I won't belabor the point. But Bay is pretty likely to continue to hit well through his arbitration years, and if he does, this deal will save the Pirates money. Nicely done, Pirates.
UPDATE: Reading over the article again, Bay says that this contract reflects a commitment on the part of the front office to keep young players around. Don't be deceived - it does no such thing. The Pirates owned the rights to Bay through the last year of the contract anyway. What the contract actually does is prevent the Pirates from paying Bay more than the value of the contract in arbitration. That's a very good thing, but that's all it does.