Some how I ended up with two empty 6000 psi cylinders. Took them in for an exchange. WOW, 375.00 dollars now for a fill & 100 a year rent. Could have been two years since I last did an exchange. While I was there I ask the fellow to weigh one of these cylinders. I know I have had heavier ones, but one of these weighed 307 pounds. I used a tiny chain hoist & the cart here at my house. The cart was given to me by Bubblerboy64 on this site. Makes it a lot easier. While I really like 6000 psi nitrogen, as i get older I have to uses tools to move them around. I can see a time coming, when I will not be able to move them around anymore. I dont know how many fills I get out of a full cylinder, but they last me over a year. They are a beast to move around.