KROK / Billfisher swivels and snap swivels by Sea Striker are the strongest swivels available.  There are two styles available; with or without ball bearings.  The KROK ball bearing swivels offer dual rotation, virtually eliminating all line twist.

All stainless steel barrel swivel

Dual rotation, all stainless steel, ball bearing swivels.  KROK Swivels are the strongest ball bearing swivels and snap swivels on the market.  Six sizes.

All stainless steel barrel swivels and snap swivels.  Unequalled strength in a compact size.  8 sizes.