A:AnswerHi Scott, the supplied handset is KX-TGA402 (not sold separately). To add or replace handset, the compatible models are KX-TGA401, KX-TGA651 and KX-TGA750.
A:AnswerThe KX-TGA401B is only compatible with the following base units:
KX-TG4011
KX-TG4021
KX-TG4031
KX-TG6541
KX-TG6531
KX-TG6521
KX-TG6511
KX-TG7531
KX-TG7541
Other than the mentioned base models above won't work with this handset.