NO! They are not interchangeable!
The CS50 (DISCONTINUED!) Replacement mic is a longer mic.
The PN 64402-11
This product is DISCONTINUED and we do not carry it!
The CS55 (DISCONTINUED!) replacement mic is a shorter mic.
The PN 72195-01
This product is DISCONTINUED and we do not carry it!
They have different headsets because they run on different frequencies.