You can use what ever size of wire you want .The smaller catches smaller bait
When you buy the wire it is wrapped with small wire which you can use to connect the trap togather.
You can usually can make 2 traps out of the bundle of wire,cost about $6 to $7.
Don't forget to cut out a door big anuff to get bait out, but smaller than door.
All you need to make this trap:Wire,pliers and something to cut wire.You can use a fishing stringer or trot line to tie to trap.(Remember the wire does cut so be careful when makeing traps.)