Primos Elk Select 4 Diaphragm Pack. - Why would you want a reed with the patented "Sound Plate" feature? 1. Your chance for success depends on how accurately you reproduce the elk language. 2. The "Sound Plate" automatically positions the call at the right angle, which allows you to reproduce both cow and bull language with one call (no more switching calls). 3. The "Sound Plate" also supports the reeds so they won't ever stretch like conventional reeds - they will last an entire season! Sentry Plate Single (Model No. 158) Cow, calf, and spike bull sounds Ivory Plate Single (Model No. 159) Cow, calf and satellite bull sounds Imperial Plate Double (Model No. 160) Cow and herd bull sounds Hyper Plate Double (Model No. 161) Estrus Cow