Best Buy offering free iPhone 5c, $100 iPhone 5s for trading in your old smartphone

In its latest attempt to rustle up iPhone(s aapl) buyers, Best Buy(s bby) is offering a new promotion, and it’s a good one: From October 13 – October 19, Best Buy will give you a guaranteed $100 credit for trading in your old smartphone, good towards the purchase of an iPhone 5c or iPhone 5s.

Best Buy currently offers the iPhone 5c for $99.99 and the iPhone 5s for $199.99 with a two-year contract. This promotion effectively renders the iPhone 5c free and the iPhone 5s $99.99. According to Best Buy, the offer is good for “any working smartphone” as long as it is “free from water damage and screen cracks.” If your old phone is determined to be worth more than $100, Best Buy will give you the difference in the form of a gift card.

Given the relative scarcity of the iPhone 5s, Best Buy will give you a rain check and honor the credit if the phone you want isn’t in stock. So if you’ve got a real dinosaur on your hands, it can pay off to trade it in.

On the other hand, if you’re looking to trade in an old iPhone, you should probably shop around. I found that places like Amazon(s amzn) and Gazelle are likely to give you more money than Best Buy.

This is Best Buy’s latest promotion to draw more iPhone buyers. Last month it offered a similar deal to clear out stock of the iPhone 5, and just last week it halved the price of the iPhone 5c from $99.99 to $50 (albeit for just a few days).

The new deal doesn’t fully start until Sunday, October 13 in Best Buy stores, but Best Buy Mobile stores started offering the iPhone 5c part of the promotion on October 10.