Been using these for a few years since they came out on the market. I prefer the flexible pot to that or the rigid FloraFlex. Good quality coco with holes on the bottom of the bag and a filter layer so coco doesn't just pour out the bottom through the holes. I rarely see and sand in my tray, though I have had fungus gnats eggs in the coco before. I just treat every bag with Mosquito bits after the roots have had a few days to get established. I would do that in any coco after seeing so many brands, to include soil have unwanted guests eggs in the medium. It has to be hard to not get them unless these are fill in a super clean facility. I don't expect that they would be. This in mass production would be outdoors, so the eggs are expected in any coco or soil.