The main benefit of a fluted mandrel hanger is that it allows the cement to return through the stack. The metal packoff, separate from the hanger, is installed after cementing. Designed with a 7-1/16" 5,000 psi or 4-1/16" 10,000 psi top TCM-ET tubing head, similar to the standard DTO, this model contains a split locknut connection between the tubing head and casing housing. Lockdown screws are used for the mechanical retention of the production mandrel casing hanger, but the system also comes equipped with a C-22 contingency casing hanger.