I have 9 E500's. Left out of 12 E500's. That I bought over 5 years ago. They work like a champ. I "re-charge" a few and place them in Ziploc bags to keep dry. Then swap them in various Cars, ammo cabinets, gun cabinet, etc. I usally have 2 - 3 in each car that sits and when the color changes, do the swap, plug in the 'used' ones for a day or 2, let it cool abot, into a ziploc. All I can say is I am happy with the purchase, clean smooth effective, seem durable enough (Of the three that have been removed from service, one quit heating, so couldn't re-charge, one was dropped 10ft to pavement and kinda cracked open and so forth, while one I dropped off the table, re-assembled, used for another year or 2, the it quit recharging.) Of the few things I recommend, this one is on the list.
