Spring outside calipers are used for measuring and transferring external measurements - especially wall thicknesses or difficult to access areas - making them very popular with woodturners.
These particular calipers is sourced from a Taiwanese specialist measuring tool manufacturer and are beautifully made. The hardened carbon tool steel arms are well-polished with well shaped and most importantly square arms (unlike many inferior Chinese or Indian-sourced versions we have all seen at much cheaper prices than this set!) - held together with a black e-coated hoop.
The threaded adjusting rod and nut are solid brass with a collet in the nut to allow for fast adjustments and the finely threaded rod provides for minute, accurate fine adjustments. It has a 0 - 200mm(0 - 8in) usable range.