The 4-pack EK-ACF Fitting (Advanced Compression Fitting) is a soft-tube compression fitting pack, they are designed for use with flexible soft tubings such as PVC, EPDM, Norprene, silicone or any other type of compatible flexible tube. EK-ACF Fitting is a more secure variant of the tubing fitting connector as the locking ring prevents flexible tube to be pulled out of the fitting by compressing the tubing wall underneath the ring. Such fitting does not require any hose clamp or similar substitute. The barb and the ring are made of nickel-plated CNC machined brass. Fittings feature quality rubber O-rings. These fittings are fully compatible with EK-AF series (45°/90°) angled adapters. These fittings sport low-profile design hence it is mandatory to secure the fitting barb using Allen Key 8mm (not included, available for separate purchase) to prevent skin damage to the fingertips - barb has no finger grip surface. PLEASE NOTE: This fitting is to be used only with correctly sized tubing! Do not use excessive force when attaching fitting barbs using Allen Key 8mm in order to prevent water block damage! Do not use any tools to secure locking ring to the fitting barb. This product should NOT be installed with any aluminum Fluid Gaming parts!