It is is not easy knowing what mull bar to use; we sell 3 different types of mulls which are offered with and without steel reinforcement. Truthfully, it can be quite confusing and I will try to make it as simple as possible.
Step 1 - Know your required design pressure (click here for more info)
Step 2 - Read the Product Approvals listed here and it should explain itself.
(hint: skip right down to the charts section)
Step 3 - Pick the mull that meets the required design pressure and then add it to your cart.
(click here for standard & steel reinforced mulls)