... ,SGS,BV4. low price, good quality5.professional manufacturer, provide technical support.Grooved Bolt is made of hot rolled ribbed bar(TR ... strength in larger diameter borholes.2. Used for permanent support in mines and tunnels.3.with pin nut device, nut could help ... ,200mm,250mm,300mm square. thickness, 4mm,5mm,6mm,8mm,10mm, and so on.