The difference between the two aftermarket filters is as I recall a difference in coating technology. The Beloptik is a hard coating that should not fail for a very long time
The original ITF does not have the edges sealed, and this allows air to get into the layers and causes oxidation.
The Maier filter has a black ring around the outside. This ring is an epoxy (like?) seal that should prevent the air from getting into the filter substrate. This should be a (relative to the original) long life filter.
At least that is the way I understood the differences.
Now, what one looses on the cost difference would likely be made up in re-sale. If I was in the market for a used PST and I did not know how old the ITF was, I would not be interested in buying it unless the seller offered a receipt that showed the ITF was replaced. If the ITF was replaced with the Beloptik filter, I would probably be inclined to pay an extra $50-$75. If it just had the Maeir, I would give going rate. If it had no record of ITF replacement, I would want it discounted to the price difference of the Maier filter.
Just me thinking about value..
My bet is that most older PST ITFs have degraded so some degree, but because it is gradual, the seller may not even realize it.
This is not a "Usage" issue. This is oxidation, and oxidation never sleeps.
Edited by Eddgie, 05 August 2019 - 02:09 PM.