UPC 52-50 is used with aluminum core duct on the plenum take-off fitting and on the duct connector. Slide clamp over aluminum core of duct. Push duct over the take-off fitting or connector. Use tool UPC 54 to crimp clamp securely. Make sure clamp is crimped as tight as possible to insure a good connection. Tuck insulation and jacket into tape ring and secure with UL 181 aluminum tape. The Unico System® Tubing Clamp, 2 in Capacity, For Use With: Aluminum Supply Duct, Black