The promo officially launches later this week (and ends on the 28th), but AppleInsider readers can take advantage of it starting today. Effectively, it pays you an additional $10 on any device trade-in valued at more than $25, which is essentially any iPhone, iPad, or relatively recent Mac that isn't completely broken.
Similar to services like NextWorth and USell that are also listed in our Trade-in Payout Guide, Gazelle's website asks you to assess the condition of the device you want to trade-in. It then makes you a cash offer and mails you a pre-paid shipping box for the device to be mailed back in ahead of payment.
Gazelle's current rates, as extracted from our Trade-in Payout Guide, for iPhones and iPads can be seen below. These prices are before the $10 bonus is added in: