Abstract: A wheel apparatus is provided for measuring by rolling contact a dimension of an elevated temperature surface. The device is particularly useful for measuring the length of product in a continuous casting machine. The apparatus includes an elongated arm having an internally cooled wheel rotatably mounted at one end thereof. The arm is pivotally movable about a mount at an end of the arm opposite from the one on which the wheel is mounted. The mount biases the arm to a position in which the longitudinal axis of the arm is normal to the adjacent surface of the cast product. The biased mount permits pivotal deflection of the arm upon contact of the wheel by cast product moving in either a forward or reverse direction. The arm has at least one longitudinal cooling fluid passage which only registers with a cooling fluid supply passage in the arm mount when the arm is in the deflected positions thereof. Generally, air is supplied through the mount to cool the arm and outer surface of the wheel.