K-9 BSD Ball Dropper 4 – 4-Ball Remote Reward System for DogsThe K9 BSD Ball Dropper 4 comes with a hanging strap that allows the unit to be hung in a Schutzhund blind or anywhere desired. An optional elbow adapter is available for $49. 95 that allows you to use the Ball Dropper 4 with the BSD wall kit, so it can be used for scent detection. The Ball Dropper 4 drops a ball with each push of the button on the remote and holds four balls. The remote can control up to eight Ball Droppers.