Monsoon G1/4" to 3/8" ID, 5/8" OD Free Center Compression Fitting for Soft Tubing, Matte Black, 6-Pack The Free Center Wrench works on the barb/base and the compression ring for hassle free installation without tearing up your fingers Physcially smaller to make mounting in tight locations; Outside diameter is just 20 mm (.78 inches) and total height is just 16mm (.63 inches) Knurled base on the barb to increase its grab when installed Precision machined entirely from brass G1/4" Thread