When you are going to buy a tree protector for the seedlings you have to plant you will need to consider various design elements.
If you are planting bushy shrubs then you may need one that has a larger diameter. Whereas, if you are planting tall slender trees such as poplars then you may need to have longer and thinner containers.
The point is you will need to consider which style suits the species and type of tree you are planting.
This is a commercial one being used to revegetate a creek near where I live. The carton is tall enough to protect the plant without being too tall.
The top 2 inches is made from a different material and allows more filtered light into the lower region of the tube. It provides an excellent shelter for young plants.
These are being used along a local creek for reforestation. They have planted thousands of young trees and they are all inside these containers.
As these were planted not far from my home I often walked over to check their progress. The were certainly securely placed into the ground as I never saw any dislodged.
In fact it was quite a lovely site to see hundreds of these containers scattered around some of the old goldfields of Castlemaine.
As you can see here they were planted on the rises and had heavy mulch scattered around for quite a distance.
Even so the plants still suffered dreadfully in the hot summer and most did not survive. I really do think about 95% of these plants did not make it for more than a few months.
It is such a shame as the planting was done by many local volunteers and was spectacularly unsuccessful.
Eventually the paper sides rotted down as did the wooden posts that were holding them firmly into the ground.
I can say I do think these are a great design and would work well IF it was possible to support the plants with some regular water at their delicate start of life. If that's not possible then I do doubt the usefullness of such an effort.