The Upgrade Consists Of: 6mm push-in fittings: Featuring positive click disengage: Configurable bulkhead fitting: Can be used as 90 degree fitting or straight per existing fitting. Now able to better fit where space is an issue: Designed to ensure you don't over tighten copper tube connection: Now suits standard 1/8 BSP fittings: ** Note: Compression nut from new design is best set up using a PZ3 Pozidriv Screw Driver: 6mm polymer airline: 50% more tube wall thickness: Stronger more resistant to cuts and abrasions: Black in color: The Benefits Consist Of: Stronger: More versatile in fitment (this addresses many application issues): 6mm is a more common pneumatic standard for fittings and tubing: Completely retrofitable for all air lockers with 3.5mm copper tube seal housings: 6mm entire upgrade kit available (Part number 171321): Black in color to distinguish from the 5mm blue tube: