I like using these:  http://www.ebay.com/itm/100-METAL-TREE-TAGS-PLANT-LABELS-ID-MARKERS-/270617549007?pt=LH_DefaultDomain_0&hash=item3f021018cf#ht_424wt_1167

But I don't use the wire hangers that come with them.  I use small zip ties and 8" zip ties.  I haven't lost one tag since using these tags.

Dennis, I use those also for some things.  Have you ever met our friend Kern?  He sells those for less than that seller: http://myworld.ebay.com/kcdeadeye13?_trksid=p2047675.l2559  My only concern with those is that there's not enough contrast to read them if I don't have my reading glasses on me.  A white tag is also easier to find amongst the foilage but won't last as long as those aluminum tags.  Kern visited here a couple of weeks ago and told me that he bought 10,000 of those aluminum tags and he's not making enough money IMO to justify that investment.

This is my permanent tag'



The are attached with a 12ga copper wire and keyed to an inventory record.