The grades and metrics of edwards products are strictly in accordance with the NHLA (American Hardwood Board Association) rules. The NHLA grading rules used in the US hardwood industry are based on imperial (inch and foot) units. But most export markets are more familiar with the metric system. In addition, the grading rules do not specify the width and length of the board. □ Standard thickness of rough sawn timber The standard thickness of rough sawn timber is expressed in quarters of an inch. For example: 1 inch = 4/4 inch. Most American hardwood sheet saws are between 1 inch and 2 inches thick, although there are other thickness specifications, but the number is limited. The following are standard thickness specifications and corresponding metric sizes: 3/4 (3/4" = 19.0mm) 6/4 (1 1/2" = 38.1mm) 4/4 (1" = 25.4mm) 8/4 (2" = 50.8mm) 5/4 (1 1/4" = 31.8mm) 10/4 (2" = 63.5mm) □ Board ruler The ruler (BF) is the basic unit for measuring hardwood boards. One ruler unit is 1 foot (length) x 1 foot (width) x 1 inch (thickness). (1 foot = 0.305 meters, 1 inch = 25.4 mm) The formula for measuring the plate ruler is: [width (inches) x length (feet) x thickness (inches)] ÷ 12 The proportion of the net facet in each grade is measured in this 12-digit unit of measure. □ Thousand feet As the name implies, it is a thousand-foot ruler (BF), the English abbreviation is MBF, 1MBF=2.36M3 single-act piston hydraulic cylinder Small Hydraulic Cylinder,Micro Hydraulic Cylinder,Linear Position Sensor,Position Transducer Wantong Hydraulic Co.Ltd. , http://www.sdhydro-cylinder.com