Compression Tee Fitting: 8 mm OD x 8 mm OD x 8 mm OD Fitting Size, Brass, 10 PK

These brass compression tube fittings have a standard ferrule (metal ring). These ferrules, also called sleeves, slide onto tubing along with a nut. The ferrule grips the tubing, and as the nut tightens, it compresses and creates a tight seal.