For over 60 years, SPI has introduced innovative products to the metalworking and laboratory industries. SPI measuring instruments are durable, precise, and reliable — all backed by an Industry leading 2-Year warranty. This set contains 30 specimens, each 7/8 inch long by 3/8 inch wide, made of electroformed solid nickel. Each type of surface finish, such as flat lapping, reaming, grinding, horizontal milling and turning, is truly and consistently reproduced to give the operator or a designer a realistic representation of the feel, appearance, and texture of the machined components.