I've been using mineral blocks for probably around 35yrs and the deer have always used them regularly but hit them the hardest around here during the off season Jan - Aug. I go to the local Tractor Supply and buy a trace mineral block for about $6.25. I use to use the Trace mineral powder from southern states and they use it just as good but it doesn't last as long as the block and is a little more expensive so i just started buying the block. I keep them out year round and replace them about every 6 months. Works for me.