PCA Elbow PCA Elbow Description The Elbows are available in 45° and 90° and insert directly into the duct system allowing for uninterrupted air flow and can be used to bypass obstructions on the ramp. REQUEST A QUOTE Contact Information Product Attributes Notes and/or comments Please check the captcha box to proceed SUBMIT REQUEST FORM Specifications Specifications Available sizes (OD): 4″, 8″, 12″, 14″ & 24″.