Beginner here. It's a great price on the perlite and nice and clean throughout, didn't find any contaminants yet. It's light for the volume. My bag is a single 100L item like you see. At the moment I am using a 70 / 30 ratio and will see how it performs. Pieces are about the size of fish pebbles, so perhaps better for the potting mixes than seed starter. There is a medium grade version too which I think could be better for that. I'm using it in an outdoor container arrangement and am hoping it will do well!
Don't forget the dust mask while working, but it's not bad if you're not dumping it out in one go. Didn't give me any problems.
By the way, the customer service took great care making sure the products got through and they arrived quickly. Extra points on that end!
