The argument might run that magnetic and the like is the most damaging
material?

Can't see the harm in fitting one, especially in older systems. So long
as they're checked/cleaned once in while.

On 11/03/2018 10:58, Brian Gaff wrote:
Which was my point. They are not really very good, and of course they rely
on the crud being able to be electrostatically charged or magnetised to
work. Stuff which has neigher quality will just go straight on.
Brian



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Cheers, Rob