Check the listing for details. Umarex Zelos FX Barrel Kit 500mm (.22/.25). Condition: New. Listed at 140.00 USD. FX barrel kit designed to fit the Zelos. This will allow you to utilize the 500mm FX liner in .22/.25cal which you would need to provide. This kit comes with everything needed besides the FX LINER. No modification is needed and it is a simple swap. Spare orings are also included. Please leave a message/note during check out to let me know which caliber you will need. The kit will come with the following: x1 stainless steel housing x1 brass barrel adapter x1 brass jam nut x1 rear shroud end cap x1 front shroud end cap (1/2x20unf) x1 carbon shroud x1 shorter hammer spring (not pictured) Note: The stainless steel housing tube does have minor blemishes. That is how I received them and I assume it was part of the manufacturing process. Note: YOU will need to source your own FX LINER