API cementing collar double stage collar with premium thread 1. Structure: 1) All inner parts are made of easily drillable aluminum alloy 2) The device can be connected directly to same type casing 3) Reliable back-pressure leak proof structure, enable grout or slurry flow with less resistance 4) Valve seat and valve disk can effectively prevent grout from flowing back 5) Hardness of base material is equivalent to API Spec N-80 6) API spec.Q1 and ISO9000 certification 2. Purpose: It be designed according to the standard of SY/T5476-92, could reduce the mixed slurry, calculate correctly, save the cement and increase cementing quality.