Board Thread:Tutorials/@comment-5885957-20121218102627/@comment-6023601-20130129124829

Crazyc92 wrote: Forcefields are impenetrable. Only 5 things can get through forcefields: catalytic lens (or lesser equivelant), wireless redstone, ender chest items, teleporters (item and player), and ComputerCraft rednet. Maybe I can find 2 other things that can get through, but not much can. If you set up your field right, not even these can get in.

Crazyc92 is right. Several things may be able to penetrate a forcefield. It is also Recommended to use both, the AFR-JT system as the first line of defense, and then the best forcefield around to protect your actual base.