ITEM NAME:Aquarium Tank Cylinder Adapter Converter for Co2 Regulator W21.8 to G5/8 Description: Material: 304 stainless steel; 4 size available: W21.8 to G5/8; G5/8 to W21.8; M22x1.5 to G5/8; G5/8 to M22x1.5 W21.8 to G5/8: Inner Thread: W21.8, Outer Thread: G5/8 G5/8 to W21.8: Inner Thread: G5/8, Outer Thread: W21.8 M22x1.5 to G5/8: Inner Thread: M22x1.5, Outer Thread: G5/8 G5/8 to M22x1.5: Inner Thread: G5/8; Outer Thread: M22x1.5 Package Includes: 1 Piece Cylinder Adapter SKU: ALU0000621364000912.Material: 304 stainless steel; 4 size available: W21.8 to G5/8; G5/8 to W21.8; M22x1.5 to G5/8; G5/8 to M22x1.5. W21.8 to G5/8: Inner Thread: W21.8, Outer Thread: G5/8. G5/8 to W21.8: Inner Thread: G5/8, Outer Thread: W21.8.