HKS SSQV BOV In 1994, HKS introduced the first Sequential Blow-Off Valve featuring a unique, pull-type, sequential valve structure and a differential pressure control system. This advanced pull-type relief system allowed for stable operating ranges from low to high boost pressures. Since imitation is the highest form of flattery, HKS has once again redesigned the physical aspects of the Super Sequential Blow Off Valve to thwart off the counterfeiters. Reliable functionality of the Super SQV 4 is unchanged and utilizes the same mounting flanges as all previous generation SSQVs. This assures compatibility with all optional HKS SSQV inserts, recirculation fittings and recirculation kits. Super SQV 4 features include a nickel-plated, die-cast metal secondary valve, which is swaged to the primary valve, a stainless steel C-Clip and spring to increase sealing and durability.