Paradox
Marine Bonsologist
I have used similar for training pots.About escaping soil - I do not think it can happen with small holes.
My smallest setting is 4 mm = ⁵/₃₂ inch = 0.15 inch and it should be less than the regular bonsai soil grade.
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The problem with them is the plastic is not treated for UV exposure for use in a greenhouse/outside. Anderson flats and horticulture trays usually are unless they are meant for one use only for sterile reasons.
So these will start to deteriorate in the sun and weather and get brittle. How many years you get out of them will depend on the thickness and type of plastic.
I would also be concerned with how thin the mesh is on the bottom. If it can't hold the weight of the soil and tree, it will cause stress and break. So you'll have to watch that too. The additional mesh will help reinforce it somewhat but will only go so far.
That said, you'll probably get a couple of years, maybe 3 before they get brittle and start to break apart. I have some trees I desperately need to repot next year because the plastic storage containers I used for cheap training pots are breaking. I've now started to buy plastic training pots for bonsai instead because they are more durable.