The Lower Stage Tool Collar Stop Assembly is used in conjunction with a packoff and Upper stage tool assembly.
Staged plunger lift is a method to get accumulated fluid from a lower depth to a point in the tubing where a plunger can effectively lift it to surface. A standard stage tool design is comprised of a bottom hole bumper spring located at the end of the tubing string, a plunger, a stage tool assembly, and another plunger above the stage tool assembly. The stage tool assembly has a dual acting seal assembly pack off to provide a seal to the tubing string and a standing valve to prevent slippage back through the spring.
The lower stage tool collar stop assembly seats the stage tool in a specific depth in the well via a standard collar stop setting procedures and absorbs the shock of the lower plunger.