Kastar HHR-P511 / HHR-P402 Battery, Type 24 &Type 30 NI-MH Rechargeable Cordless Telephone Battery 3.6V 1800mAh, Replacement for Panasonic HHR-P511, HHR-P402, P-P511 (Detail Models in the Description)

Fit into a handheld landline cordless phone. Works.

These Kastar batteries are excellent replacements for genuine Panasonic batteries. Like the Panasonics, they are essentially three 1.2V rechargeable AA batteries assembled together to create a 3.6V battery. The price for rechargeable 1.2V NiMH batteries in 2016 is slightly more than $2 apiece, so the Kastar is fairly priced. Genuine Panasonic costs about 3x as much - ridiculous. Kastar works fine. They were shipped promptly, and arrived in perfect condition.

These replacement batteries fit perfectly in my old Panasonic phone system, work just fine and so far seem to do a good job of holding a charge. These are hard to find, so I was happy to see them on Amazon.

The OEM battery that came with my Panasonic KX-FPG 389 fax-phone combo 15-20 years ago lasted for several years. By the time I needed a replacement, Panasonic wasn't making them any more. Of two Kastar replacements I ordered a few years back, one died after just a few weeks so I thought about dumping the phone. The Kastar batteries today seem to last longer and extend the life of my ancient relic another year or two at a time. An extra star to Kastar for actually continuing to make batteries for an obsolete product.

I’ve been trying to find a rechargeable battery for my old telephone/fax and decided to try this unknown brand. I’m loving it. Reasonably priced.

They replaced my old batteries in my portable phones, two of them.

Same as any other. Nothing special.

I was warned that ordering a land line phone battery was fraught with problems -- false data. I ordered a replacement batt for my Panasonic land line wireless phone, it arrived promptly and fit nicely in my hand-set, and charged up right away when parking my handset in the phone set and it works just like new. Kastar is my fave for batts!