Metalwork Brass Hose Barb Fitting, 6mm Barb x 4mm Barb Reducing Splicer Mender Union, Air Water Fuel Hose Reducer Joiner (Pack of 2): Amazon.com: Industrial & Scientific
Brass Male Hose Barb Fittings
Amazon.com: Brass Hose Barb Reducer, 3/8" to 5/16" Barb Hose ID, Reducing Barb Brabed Fittings Splicer Mender Union Air Gas Water Fuel Line Heater Garden Pond Poly Tubing Adapter (Pack of 2) :
Flo-Link XL Double O-Ring x 2" Brass Hose Barb Adapters - Set of 2 - Geo-Hydro Supply, Ltd.