Genuine Acme Alpha 210.5 (Black/Orange), Acme 210.5 (Khaki or Black) or Acme 211.5 (Black) Whistle with Lanyard Whistle training remains one of the most effective means of distance-training your dog. Acme have been producing quality dog whistles since 1860 and invented the silent dog whistle in 1935. Works well with all dogs,both good for distance and close work. 210.5 especially well proven with Spaniels, and 211.5 especially well proven with Labradors