our company is the professional manufacturer of core drill barrels.please notice that our core drill barrels are half finished(without diamond segments). our main target customers are manufacturer of diamond core drill bits from Korea,USA,Japan,Russia. the specification scope 1,the diameters are from 10mm to 920mm 2,the lengths are from 100 to 1600mm "3,the thread type are 1 1/4""-7UNC,1/2""BSP,5/8""-11,M32,M27,M22,M16,M14 and so on" there are also some adaptor and extension our website is www.hhdiatools.com