Shenlong manufactures all the four types of subs e.g. straight od type a or reduced section type b or swivel sub type c or lift sub type d as per api spec 7. \n\nthese would be with box and pin connections or with box or pin connection on both sides. class of subs manufactured are (a) kelly subs (b) tool joint subs (c)crossover subs (d) drill collar subs (e) bit subs (f) swivel subs (g) lift subs. bit subs can be bored out for installation of float valve assembly.