Mountain Air 0416 4-Inch Carbon Air Filter – 310m/hr High Efficiency, 100/400 Grade – Ideal for Grow Tents, Hydroponics & Indoor Air Purification (Revolver 357 Compatible)

I'm dinging this two stars straight away for the following reasons:1) - Very poor packaging, the great build quality is sadly it's own undoing as it's not packed well enough for the weight and quality build.2) - The filters are not washable, they were full of charcoal so I went to wash them and they're toast, totally worthless now.3) (Maybe) - Mine came VERY banged up so I don't know if the hole at the top isn't sized properly for a 6" fan of if it is too distorted from shipping damage.With that out of the way, this thing is a BEAST!!! Look at it next to a VanTech, nothing even close to the same, it's like 2.5 filters in one! I took the top and bottom off and spent an hour reshaping it after shipping damage and can tell y ou it's very very well built! I did get this on a warehouse deal so I knew it was damaged (likely got more damaged coming to me) and didn't mind putting in the work for the discounted price. It afforded me the chance to open it up and I wouldn't hesitate to buy one again having looked at it in depth.If it weren't for the two easy to fix issues this would be 5+ stars in my book. The filter not being washable however is a major flaw!The packaging is very minimal from the factory and it doesn't come inside of a second box like most Amazon purchases. This means the closed end and flange are badly dented, making an awkward seal with typical duct clamps.Quality otherwise seems great. Very heavy and huge. The prefilter isn't a bag like would be preferred, but instead polyfill like insulation that flares out towards the ends so it can't fully do it's job.Only reason im giving it 4 out of 5 is that because it got dented slightly during shipping and but i did get the package same day delivered. Overall the filter looks nice and is working so far.