Ignoring the ageing effects on some filters.
Older filters were good for ADSL but their high frequency characteristics were not optimised for VDSL although they would still work. Users may often see lower than expected results.
There are a variety of filters out there - some cheap and some expensive and some a real rip off! If you are not too worried about getting the best possible speeds than a cheap filter off ebay will suffice, however if you want the best possible performance, hopefully another member here will be able to suggest the best options.
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