Aluminum Cross Connects - Purlin Clamps for Greenhouse Product Description Name: Greenhouse Cross Conntects Hoop Size:1 3/8", 1 5/8", 2"[1-7/8" O.D.], 2 1/2" [2-3/8" O.D.] Purlin Size: 1 3/8", 1 5/8" Material: Galvanized Steel or Aluminum Alloy Feature: Yokelink Aluminum cross connectors are used to tie together two pieces of pipe in the greenhouse structure or any other application