1. The black one is the newer model, stronger and less sound.
2. The old black foam top remote is/was to be used no more than 3-4 days. After that, whatever bugs survived became stronger. People would forget this and would use it too many days and also people would forget this black foam top remote was only to be attached to the MN port on right side. Due to its polarity if put into the BN port on the left side, the person may receive zero benefit.
This seems to be too much for people to remember.
The white foam top remotes and the new clamshell type remotes do both healing and killing programs.
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