Differences in Micro-filter(s) MF

[#1]

Most filters that I have personally had supplied by ISP's & or my clients have had supplied are
35MF
I was just sorting out stock of a mixed batch of brand new BT branded filters & have come across some that are
50MF
What is / are the differences & which would give the best results / (uner what type of conditions (IE: long / short lines / REIN)) etc
As they are new, & for sale to client(s)
I do not want to open any up for testing

[#2]

I think you will find that the 35MFs are filters made by D-Link, whereas the others sound as thought they are MF50s made for BT by various manufacturers. BT have a general spec. for filters, can't remember what the reference number is but the MF50 spec. will be based on that.
AFAIK there's no specification that says one particular filter is for certain conditions and it would be very much down to trial and error and user experience, even two similar length lines can have very different performance in practise.
Different manufacturers try and produce filters that they'll claim are better than there competitors, but that's not always the case. Have a read of this adslnation article which will give you a better idea about different filters. Obviously steer well clear of those "low cost" filters if you want good ADSL performance.
Edit: you might get adequate performance from a "low cost" filter on a very short line!
Edit: Attach pdf of adslnation page in case link dies in the future.

[#3]

That link is pretty old and I am not sure whether the latest BT Filtered Faceplates are better than the ADSLNation ones or not  - the ones they fit when you get Fibre

[#4]

You are quite correct Jim, but he did ask about 2 specific Rat's-tails type filters. The link may be old, but the information is still valid and unless you are plugged in at the master socket, ADSL(2+) users are still likely to want microfilters. I did consider attaching a print of the adslnation page in case the link dies. As I have one handy, I'll probably do that before my edit time runs out