Testo 0613 4611 pipe wrap probe with velcro testo 0613 4611 p this pipe wrap probe from testo can be used to carry out surface measurements on pipes with a diameter up to 75mm you can use it to determine the surface temperature of heating pipes for measuring flow and return values it is suitable for use with any testo product that has an ntc sensor input p the ntc sensor is attached to a wide 300mm long strip and the velcro fastener on this strip enables the surface probe to be attached