The Supertech black-nitrided intake valve set for Ford EcoBoost 1.6L includes eight intake valves and the source advises use with keeper KPR-50 / 7S. These nitrided intake valves are specified for the 1.6L EcoBoost valvetrain and the keeper recommendation is provided as part of the product listing for correct assembly.
Supertech Ford Ecoboost 1.6L Black Nitrided Intake Valve - Set of 8 (Use w/Keeper KPR-50 / 7S)