Make sure it is not continuous current.
If you have a lowes near by you can put together your own kit for just a few dollars more than those kits.
ss-550 which is a pulsed current 1 sec on 1 sec off -- 58.00
step in temp post -- $2.00 each
10 to 20 feet apart
-- these work great for temp fences -- metal post with plastic insulators are better for perm installations.
250 feet of aluminum wire about $4.00
For temp use I hang the energizer on the pole and hang a 5 gallon bucket over it.
You can also use it to contain the chickens & ducks -- once trained they will avoid the wire.
BE CAREFUL with continuous current energizers with small animals like cats chickens, ducks -- will get shocked but not able to get away -- they looked glued to the wire -- the pulse energizers allow them to get shocked and then get away.