Um, not meaning to sound like a jerk, but I would have asked that question before I bought them....
Let me know how they work for you. I've looked at them plenty of times but have the same concerns you do. From everything I've heard they're hit and miss.
Si vis pacem, parati para bellum
"Any man who thinks he can be happy and prosperous by letting the Government take care of him; better take a closer look at the American Indian."