Serviced by DOT certified / licensed service center - weighed and ready to install - ground shipping, new hydro. We trade work for and / or buy cores also. We service cylinders for many companies in many states and are very thankful. You can't get any closer to a full lifespan on your hydro unless you do them yourself. Some cartridges are a year or more older when bought off the shelf, however we hydro them when you order. We can rebuild your old cartridges, increasing your profit margin. We can even put your company info on ea. cartridge. Thank you for looking! WE BUY EMPTIES/CORES. WE ALSO TRADE CORES TOWADS REBUILT ONES AND OR REBUILD YOURS. Prices going up as core prices go up.