Variable ND filter, compatible with 49mm lenses, allowing for light adjustment. - Brand: K&F CONCEPT - Model Name: NANO SERIES FILTER - Filter Type: Variable ND Filter - Size: 49mm - Included: Dedicated case Thank you for viewing. There are fine air bubbles on the surface, possibly a defect or part of the specifications. I didn't feel it affected the photos much. I took it to a camera store, and they confirmed it wasn't mold, so that should be fine. Please consider this, including the above. Thank you.