Proline Series 1/4-in x 1/4-in Compression Coupling Union Fitting in the Brass Fittings department at Lowes.com
Ideal Vacuum | Swagelok Tube Fitting, 1/4 in Ferrule Set, Gaugeable, Stick of 10 Sets, Monel Alloy 400/R-405, PN: M-400-SET
100pcs 1/4 Inch Tube OD Brass Compression Sleeves Ferrules Brass Ferrule Fitting | eBay
LTWFITTING Value Pack 1/4-Inch OD Brass Compression Union,Sleeve Ferrule,Nut (Pack of 85): Amazon.com: Industrial & Scientific
3 mm Diameter Compression Fitting with 1/4" NPT Fitting for RTD Probe | Evolution Sensors and Controls
Amazon.com: 304 Stainless Steel Compression Fitting Ferrule, 1/4" Tube OD x 1/4" NPT,3/8" Tube OD x 1/4" NPT,3/8" Tube OD x 1/2" NPT Male, Straight Adapter Connect with Ferrules (NPT1/4-1/2"OD) : Industrial