they screw down to the deck from inside the base, nothing on the outside but with a bit of sealant on the bottom to seal the base unit (you can't see the sealant obviously when fitted). They are the single version like this js6s Jockey Consoles/ Seats for use in RIBS and open boats
but all white with pearl grey piping. Still trying to decide whether to keep them. although they are singles there is room for 2 on them although i don't.