They're just ordinary shoe trees, Left Hand. Made by Woodlore, if memory serves, and pretty much the same as the trees Allen Edmonds sells on its website. There's nothing uniquely wonderful or awful about them.
I suppose if you jammed a large shoe tree into a relatively small shoe, the tree might stretch out the shoe. But that's likely true no matter what the make of shoe tree; it's not as if it's purely a JAB thing.