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) :
Amazon.com: 5/16" Barbed x 3/8" NPT Male Adapter Brass Hose Barb Fitting 5pcs : Industrial & Scientific
CARBURETOR FUEL LINE ADAPTER 3/8" MALE x 5/16" FEMALE INVERTED FLARE | eBay
5/16" Flare x 3/8" Male Brass Adapter - Warren Pipe and Supply
Triad-Orbit 5/8" to 3/8"-16 Camera Adapter 3/8ADA B&H Photo Video
5/16" Compression x 3/8" Female Brass Adapter - Warren Pipe and Supply
Amazon.com: Reducer Hose ID 3/8” to 5/16" Brass Barb Fitting (2 Units) : Industrial & Scientific
LTWFITTING 5/16 in. O.D. Comp x 3/8 in. MIP Brass Compression Adapter Fitting (5-Pack) HF685605 - The Home Depot
Carburetor Fuel Adapter 5/8-18 Male x 1/2-20 Female ( 3/8" x 5/16") | eBay
Watco® Brass Adapter Pin - 3/8"-16 And 5/16"-18 | HD Supply
Lead Free Brass Compression Male Adapters - 5/16"T x 3/8" MIP