SeaKing Stores › M12 x 50mm A4 stainless socket-cap bolt - EACH M12 x 50mm A4 stainless socket-cap bolt - EACH £1.10 M12 thread diameter x 50mm length. A4 stainless steel socket-cap screw. Sold individually; quantity 10 means ten loose bolts. Add To Cart Added! M12 thread diameter x 50mm length. A4 stainless steel socket-cap screw. Sold individually; quantity 10 means ten loose bolts.