I WOULD CHOOSE MODIFIED CHOKE FOR SLUGS. IMPROVED SHAVES A LITTLE LEAD OF THE SLUG, JUST A LITTLE TOO TIGHT,AND CAN THROW IT SLIGHTLY OFF TARGET. RIFFLED CHOKES ARE FOR FOSTER SABOTS. EVERYTIME I'VE USED A RIFFLED CHOKE, IT PUTS A BIG SPIN ON THE SLUG. AT 50 IT'S HIGH, 60 IT'S RIGHT, AT 70 IT HITS LOW. IT HAS TO BE FULL RIFFLED BARREL OR NOTHING. WITH NO CHOKE, YOU DON'T WANT TO DAMAGE THE THREADS. MODIFIED CHOKE FOR RIFFLED SLUGS IS THE BEST CHOICE.