Formufit 3/4 in. Furniture Grade PVC 3-Way Elbow in White (8-Pack) F0343WE-WH-8 - The Home Depot
Formufit 1-1/4 in. Furniture Grade PVC 3-Way Elbow in Black (4-Pack) F1143WE-BK-4 - The Home Depot
FORMUFIT 1/2" 3-Way PVC Elbow Furniture Grade Fitting in Black, 0.84" Actual ID, (Pack of 10), Made In USA, UV-Resistant, Impact-Proof, Easily Build 3-Point Corners with PVC Pipe - F0123WE-BK-10: Amazon.com: Industrial