I bought these about 5-6 months ago and used them for tracking filters. Super nice and practically inaudible. I really love these but I don't need 4 of them. The thing that I like most is that there is no weird phasing issues and it gives you more head room depending on how much you cut off. Not many options for 500 series high and low cut filters unless you drop 500 on trident audio and that's just for 1. These come from Canada which might mean you have to pay a big chunk for tariffs and what not if you buy from them. 100% Positive Feedback Seller. Fast Shipper. Usually same day if ordered early enough in the day and not on a weekend or holiday. No returns whatsoever. If you need confidence in making a purchase from me just look at my feedback. Cheers!