On sale! (normally $10) The EK ACF Fitting (Advanced Compression Fitting) is a soft-tube compression fitting, designed for use with flexible soft tubing such as PVC, EPDM, Norprene, silicone or any other type of compatible flexible tube. The 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.