3M Sv-Spf1 Type 1 Fine Particle Filter Cartridge

When making a decision to buy this Type 1 filter or the type 2 filter, consider what it is you're cleaning. If it's professional use, a type 2 may be what is needed. But I use this filter to clean out my hepa filters (large Sharp units). So having a Type 1 makes sense because what's the point of cleaning extremely fine particles out of another hepa filter if I'm just going to put them back in the air?I have two of the largest Sharp units in my home, and I clean them out once a month. Even at that rate, each month it's like removing a link blanket that covers the entire pre-filter. So this filter is great for my needs.