The post is from Builder Supply in Omaha, NE. It is a post normally used with stairs.
The construction;
We chopped them to size as they were much longer than we needed and because the quartz slab was maxed out, we had to support it much more than with two posts. We fabricated horizontal pieces to each post by making notches in the posts to receive the "headers" if you will...like a beam. Also, did the same on the return back to the island cabs. On the cabinet side we used a 1x ledger to receive the center return/ beam...nailed & screwed, glued, filler and finished with paint and veneer strip to bring the horizontal piece out flush with the post finish. Hope this helps!