SPAX combines a fully-threaded shank (for most versions) with a patented serration pattern, a patented head style called the MULTIhead, which countersinks the head flush with most materials, and a patented point called the 4CUT ™ which eliminates pre-drilling and splitting because of its square end which divides wood fibers.
That combination of the 4CUT ™ point and serrated thread is effective enough to eliminate pre-drilling unless you're driving into either masonry or sheet metal better than 24 gauge. SPAX ® have the German building code approval.
The Double Threadlok feature of the SSX series screws is designed to thread into both boards in a wood deck flooring application. It eliminates screws from backing out and squeaking as lumber dries out.