WHEEL MEASURING 4" SINGLE WHEEL (FT, IN). This Keson measuring wheel is lightweight, reliable and high quality used in indoor and short term applications. It is compact and easy to use for measuring horizontal, asymmetrical and curved surfaces. A differential is that one of the wheels can be used as an emergency backup. It has an extended, easy-to-read 5-digit counter of about 9,999 feet, 11 inches, without resetting.