This "semi covert" design or earpiece/mic. has a transparent plastic "audio tube" earpiece, so it less obvious that an earpiece is being worn.
It also has a separate lead to the microphone. This means that the microphone can be positioned more easily, for example in the wearers hand, with the lead running down a sleeve.
This design of earpiece/microphone is popular with people doing security work.
The Kirisun walkie-talkies generally use either the "K1" Kenwood twin-jack socket, OR the "M1" Motorola twin-jack socket.
The PT558, PT4200, PT5200 all use the Kenwood "K1" socket.
The PT568 used the Motorola "M1" socket.