Quality barbed fittings provide high retention in low-pressure poly tubing for long-term reliability of connections. The acetal fittings can be confidently installed without clamps when matched with our quality low-pressure poly tubing with corresponding dimensions. See note below on gray PVC fittings.Features:Sharp-edged barbs create leak-proof sealIncreased strength and superior qualityHeat, chemical and wear-resistantUV stabilized materials for long lifeSpecial Note: 1/4" barbed fittings have the unique ability to be "snapped" into larger tubing after punching a hole into the side of the larger tubing with any of our 1/4" punch tools. This creates a water-tight seal and allows you to "tee-off" of larger diameter tubing using only 1/4" fittings and a hole punch. A Barbed Tubing Coupler is used to connect two pieces of low pressure poly tubing of the same size in a straight line. Please Note: Gray PVC insert fittings are made of the same substances as schedule 40 and schedule 80 PVC are made of. This means a durable long lasting fitting. Insert fittings are normally used with flexible pipe, hose or tubing. Simply slip the barbed insert tip all the way into the end of the flexible pipe, hose, or tubing. Multiple sharp barbs provide a tight grip on the flexible materials to create the seal. It is recommended to clamp over the barbed fittings to provide a reliable leak-proof seal. Proper clamping technique is to place the clamp directly over the barb area and tighten. For additional size specifications see the Spec sheet linked to item page above. Fitting SizeAcceptable Inside Tubing DiameterFitting UseMax Operating Pressure1/8".125"To connect sections of 1/8" tubing or to connect 1/8" tubing to mainline tubingUp to 30 PSI1/4".170"To connect sections of 1/4" tubing or to connect 1/4" tubing to mainline tubingUp to 30 PSI1/2".570" to .620"To connect sections of 1/2" poly tubing togetherUp to 30 PSI3/4".805" to .820"To connect sections of 3/4" poly tubing together