Have empty 60L CO2 cylinders, but no box? Want to join the Drinkmate CO2 exchange program?  Get a specially designed Drinkmate CO2 Exchange box mailed to your doorstep. Send back up to 18 empty cylinders*! Free Shipping! We will include a prepaid return label and instructions in the box. We accept Sodastream and Sodasense threaded 60L cylinders in our exchange program! *If you have between 9-18 cylinders to send back, choose the 18 pack option. Please specify in the order notes how many cylinders you have to return when choosing this option. If you have between 5-8 cylinders, please order the quantity of 2, 3, and 4 pack boxes needed to send these back in two boxes*  No sign-up required! At Drinkmate we give YOU the option of how many empty cylinders you'd like to send back, or how many filled cylinders you'd like to order. Plus- the more CO2 you order, the more you save! More information on Drinkmate's CO2 Exchange program can be found here.  Includes the return box and return label only, no CO2 cylinders are included! All orders placed on idrinkproducts.com with more than one CO2 cylinder will automatically include a return box. There is no need to purchase one additionally.  Contact CO2@idrinkproducts.com if you have any questions. Cheers!