Hi Mark, it sounds likely that you have a Radical ST binding. If it is all black and gray, you have a Radical ST, if there is some green and bronze color to it, you have a Radical ST 2.0. We currently have both in stock, and you can select the one you need from the drop down menu above.
I'm sorry to hear that you've broken several of these. It seems that if there is going to be a failure of the Radical ST binding, that the heel piece is the weakest link. That being said, we have many customers who have never had a problem so it seems to be hit or miss as to whether or not its an issue.