Choose ecosmart™. Lightweight and portable, these cylinders provide the high quality and stability needed in today's workplace. ecosmart™ cylinders come in a variety of sizes to suit your calibration gas needs. The ecosmart™ program solves the issue of what to do with empty cylinders. Returning cylinders is simple and FREE. Each ecosmart™ cylinder is sold with an M/T plug. When the cylinder is ready to be returned, install the M/T plug to release any resigual gas. Request a prepaid label by going to www.gascogas.com and clicking on the ecosmart™ 'Returns' button. Complete the form and print label. Prepare a box with adequate packing material and ship to Gasco. ecosmart™ cylinders make earth sense - reduce, reuse, and recycle!