Rockwool

At first they looked smaller than I expected, but they work great. Retains a lot of water. I chose to germinate lettuces in a block of cubes, then plan to rip the cubes apart later. Otherwise the lettuce seeds tend to fall between the individual blocks if you rip them apart first.

Perfect

Tiny. Be warned. One complaint is they tear apart easily. My own fault ordering them.

These Rockwood cubes work great they fulfill their purposes very well. I just poured my chili seeds on top of the whole cube because it was too difficult to put them in each hole. They sprouted tremendously and worked great under inside lighting, but grew phenomenally outside.

These were very small. They did not fill my gardyn cubes. I also did not have much luck getting seeds to sprout. Picture 1, the seeds have been planted for over 2 months. Pic 2 shows how small they are. I had to make holes for the seeds as there weren't any.

These rockwool cubes are a good quality for the price. it has a decent water retention and works well to germinate seeds. You do have to be careful separating them as I have split a few in half, but when I smushed it back together and put it in the hydroponic pod they still worked as it should. I start mine hydroponically and then I transition them to my garden where I leave the rockwool on and I haven't had an issue. Easy to use and I recommend these.

These are easy to use and sprouted seeds quickly.

Not sure if it has fiberglass but not the same quality as the real rockwool had Itching prickling sensation