OCTG with premium connection has the same performance as HSC,VAM,NEW VAM ... , 2T, 3T FJL(4T ),NF6, NF4,HOOK(5T),BIG(6T) premium connections,which has the same performance as HSC,VAM,NEW ... have got the chinese national patent .The application scope for premium connection includes 2 7/8-20,suitable for the steel ...