4.5" Stamped Steel Chassis JK Products 2521NP 4.5" Chassis Solid $14.95 JK Products 2523NP 4.5" Chassis slotted. Same as 2521NP but with a slot in the middle - more flexible $14.95 Parma 596 4.5" Flexi-2 $16.50 Parma 606 4.5" Flexi-3. $16.00