chengJellyLibrary 10/30/50Pcs PM2.5 Activated Carbon Filter, 5 Layers Replaceable Anti Haze Filters, Protective Mouth Filter for Outdoor (4 Layers 50 PCS)

Easy to use and great value.The "cat" loves the way that her litter tray is readied so quickly, after she's left me a gift.

I received the 50 PM2.5 filters that I ordered, they are 4 layers instead of 5. But more alarmingly, the single layer in front of the carbon layer seems to be made from a material that feels 'plastic' to the touch. It is IMPOSSIBLE to force/blow air through this single layer, never mind attempting to breathe through that layer. Therefore the filters cannot be used. I cannot comment on the quality of the remaining 3 layers as I am not an expert.The seller offered me a 50% refund, I refused so he gave me a 100% refund. Reading other reviews I think that this seller is sending out a mixture of genuine filters and fake filters, and he obviously knows this and is continuing to do so.