With this package you are getting the heating element and all the thermostats on the dryer.
The 279838 heater is rated at 5400 Watts 240 Volts and has 2- 5/16" male terminals.
The 3977393 is a 325F Thermal Fuse, it is a non resettable fuse.
The 3977367 is a L221F Thermostat that mounts onto the Heater Housing.
The 3387134 is an Operating Thermostat rated at L155-25 differential, with a 120 Volt 2 Watt Heat Anticipator.
The 2 outside terminals are 1/4" male & the 2 inside terminals are 3/16" male.
The 3392519 is a thermal fuse is 91C / 196F & has 3/16" terminals, please check yours some have 1/4" terminals.
This fits specific Whirlpool manufactured dryer models including Kitchenaid, 110. series Kenmore, Roper and Estate.