I have one - it works well. If you're familiar with other bottom button
mods it's very similar. I would not recommend standing it up on the end though, as part of the end cap is cut out to allow the bottom activation, which means it's not stable. Personally, I recommend always laying your ultramax on it's side anyway, as they're very light, which means they're easy to knock over. This helps avoid any damage to your RES.