Mazdaspeed Seats.
Images:
Synthetic Leather 'Sport' seats come in Red, White or Black with the Grey MS centre. White and Black most common.
'Type-F' Suede ones come in Navy Blue, Black, Red or Grey. Black most common.
Rails are built-in to the seat - and therefore they are a universal rail - but there are car-specific brackets that attach to each corner of the rails.
They are now unavailable new, as they (along with many older MS parts) have been discontinued.
Secondhand ones will appear below, and generally sell for about 15000-40000 per seat, or 40000-80000 a pair (depending on condition of course)