Convenient design: leaves swing out for use and fold back away in holder for storage Use to determine the pitch of a thread that is on a screw or in a tapped hole Leaves are made from durable stainless steel For internal and external threads 28 leaves fit a wide range of pitches from 4 to 80 Used for measuring inch-pitch screw threads. Leaves are made of durable steel. Convenient design: leaves swing out for use and fold back away in holder for storage. 28 Leaf steel screw pitch gage: 4 to 80 TPI range, 60 degree thread angle. 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.