The Primex 90° Squeeze Elbow (EB4X90) offers a venting solution for tight 2×4 wall and ceiling spaces. Designed to work well with the Primex WG4, WGX4S and RDV4 air diffuser products, this unit offers a fast rough-in for quick and easy installation. - See more at: http://www.primexfits.com/hvacventing/product-type/without-screen/#sthash.GyPC1Rpu.dpuf