Hi, we used non Fix-all silicon used for glass in a couple of plots in Manaos, Brazil and some plots of Peru. This silicon worked very well filling the leaks between the collar and the tree stem. The only problem is that with the time the silicon loses his capability of attaching. We tried with several kinds of silicons (for wood, plastic, glass, and have the same results. I do not know if Fix-all one mantain the tube attached all the time (as it is showed by GEM manual) but what I suggest is using something for extra-attaching like square pieces of inner tube plus strapping band and springs (as used by dendrometers). This extra thing does not affect the measurement and give you long-term attaching. Hope this helps.