At TomatoInk, buy one refurbished HP 950XL / 951XL-Compatible Inkjet Cartridge 4-Pack for $39.96 and get a second one for free via coupon code "TI950DN". (Add two 4-packs to your cart, then apply the coupon.) Shipping adds $3.99, or spend over $50 to qualify for free shipping. Each 4-pack features one each of black, cyan, magenta, and yellow ink cartridges. A 1-year TomatoInk warranty applies. Deal ends August 4.