WPO23 Steel Zirconline® – Tree of Life Hoops These great hoops are sold by pair. You can wear them in your lobes and tunnel too! They are made of stainless steel and the thickness of the pin is 1.0 mm. The diameter is 55.0 mm. The length from the bridge to the longest spring is 90.0 mm. You should take them out before showering and go swimming.