I'm not even close to an expert on bindings, but I'm pretty sure those won't work with the Custom. They should say EST in the title of the bindings if they are Burton's system. And I'm pretty sure that all the Burton Customs have to have the EST bindings.
Hope this helped and let me know if you have any other questions.
Those bindings will work with the channel on the Custom but you'll need to get adapter discs from Burton. You'd be better off with an EST binding but they are going to cost more. The Freestyle is an entry-level binding, consider saving up for a better binding.