This super strong, stainless steel Herm Sprenger prong collar is widely considered to be the best dog training prong collar on the market today. Other companies may make prong collars, but none come close to the quality and performance of the Herm Sprenger line of collars. The 1.6mm, 2.25mm and 3.25mm have an o-ring and a swivel. The 4.0mm has two o-rings.
SSP2 2.25mm, 14in/38cm Stainless Steel - $26.95
SSP3 3.25mm, 23in/58cm Stainless Steel - $33.75
SSP4 4.00mm, 26in/65cm Stainless Steel - $39.95
Safety Notice: Prong collars can come unhooked at any link point. Therefore, it is also recommended to have a backup collar on the dog in addition to the prong collar. Dominant dog collars make excellent backup collars. Simply clip the leash to ring on the prong collar and the live ring on the dominant dog collar. That way if the prong collar comes unhooked accidentally, your leash is still connected to the backup collar.