PrimoChill Rigid Revolver Compression Fitting - Straight Knurled Grip - For 3/8in. ID x 1/2in. OD Tubing (4 pack), Nickel Plated Brass - Black Lightweight, low profile, patent pending design Nickle Coated Brass interior Interior Compression O-ring Bright Aluminum Colors, or Nickel Plated Black and Silver Designed to work with PrimoChill Rigid 1/2 OD tubing. 12mm Tall (Cap height when installed), 24mm Round