Abstract: An apparatus is provided for determining a type of insulation for a first pipe and a second pipe having a first predetermined cross-sectional wall thickness a second predetermined cross-sectional wall thickness, respectively. The apparatus includes a ruler sheet having a bar situated thereon. Also provided is a pair of scales each including a plurality apertures formed therein through the ruler sheet and a unique inner diameter indicia situated adjacent each aperture. Such pair of scales include a copper tube scale and a iron pipe scale situated on the ruler sheet. The apertures of each scale are offset a predetermined amount to compensate for the difference between the first and second predetermined cross-sectional wall thickness.