lifting sub, API standard lifting sub 1API spec7-1 2for lifting of the drill tools 3divided into a or b type structure 418 or 90 degree shoulder lifting sub is a special tools for lifting of the drill tools in petroleum, natural gas industry and geologie exploration. Drill tool lifting sub is divided into a or b type structure. The a type has 18 degree shoulder, the b type has 90 degree shoulder. The lifting sub can be selected according to elevator structure. Integral lifting subs are made of high strength alloy stell. All connections are complied with API spec7-1. Welcome your inqury.