afe Magnum FORCE Intake Coupling Kit (3-1/4 IN ID x 4-1/2 IN L) Straight Bellow-Coupler - Black3 1 8 IN Internal Diameter: This 4 1 2 IN long coupling is designed to connect to a tube with a 3 1 8 IN diameter. It's commonly used on aFe POWER cold air intake systems, but can be used for a variety of projects. Flexible Bellows Silicone: Its bellows design is extremely flexible, making it easy to install, even when dealing with misaligned tubes. It allows for ample expansion, movement and vibration in between two hard pipes. The built in port