Decided to go with the new All Pro 12-4 instead of the 12-1. They have the exact same design. The only difference is the 12-1's are 3/4" thick. The 12-4's are just over 1" thick. If I ever decide to go twins or vortech brings out a bigger blower. I'll have a motor ready for it. I need all the clamping force I can get.