How to place an order?1, Choose the outer diameter and length, comparable to "coupling GFZ": if I want to purchase outer diameter 30mm and length 50mm, then I prefer GFZ-D30XL50.2, Pls write the inside diameter size on the order page.3, If you can't discover the outer diameter and size size, pls choose different size or contact the seller. Normal all size chart we can make for you.Hot items hyperlink