... 43A ) BS729 AustraliaAS1657-1992 AS3679 AS1650 2.Bearing Bar Sizes: 1"x1/8",1-1/4"x1/ ... ,35.33mm,38mm,40mm,41.25mm,50mm,60mm4.Cross Bar Pitches: 38.1mm, 50mm, 75mm, and 100mm ... kinds of steel gratings distinguished by different bearing bar types.The respective of features are as follows ... stair tread,etc.Serrated:Better non-skid property & safety compared with plain grating.I-Shape:lighter,more economical ...