Extra Heavy-Duty with thicker blades and stronger joints than the standard model. Your Choice of Scales: English model - Graduated in feet, 10ths, 100ths. Regular outside markings in feet, inches and 16ths. Red foot figures. 6' x 5/8" Metric Model - Graduated in millimeters with centimeter and meter markings on metric side: English side marked to 1/16ths Lufkin Red End Engineer's Folding Rule - Heavy-Duty Models luredendenfo$15.50, 6/$85.50Scale: 1066D English1066DM Metric Need more information? Please feel free to contact us at 1-800-592-6940 - Ask for Extension 547 or Internet Sales.