Use common sizes, wall thicknesses, and grades of material. Tube and pipe charts available from any tube and pipe supplier show all sizes that can be made. Many of those sizes are available only at a premium because they are so seldom produced. If you are not aware of the sizes and grades commonly produced, check with a tube or pipe supply house to see if the product you have in mind is normally available. Examples of tube and pipe sizes found on charts that cost more because of their rare usage include 4-1/2 inch pipe (measures 5 inches outside diameter [OD]), 11-inch-OD tubing, 9-inch pipe, or 7- by 4-inch rectangular tubing. The use of odd-sized materials can double your material cost and easily double bending cost because your supplier may have to build or modify tooling to perform the odd job.