The Acme 212 Protrailer Whistle is the professionals choice with a constant frequency no matter how hard or soft you blow which is a big advantage in competitions or for highly trained dogs. Small high pitched whistle, made in England. Ideal for terrier and border collie type dogs, but is truly universal.Protrailer Whistle FeaturesMade in EnglandSmall but high pitchedNo peaProduces a solid, single, high-frequency toneAvailable in black Acme\'s Ref. MPN: AC212Colour: BlackSizes: One SizePM Ref: 209426