Primos Hunting Calls. Primos Imperial Plate Double Sound Plate Mouth Call. The 30 degree angle in the Sound Plate, double-reed design, and "V" cut in the bottom reed make the Imperial Plate Double perfect for reproducing cow and herd bull sounds. The "V" cut also adds the raspy sounds of the herd bull's growl, bule, and chuckle. To thin latex reeds. Primos Model No. 160. Primos Game Calls Imperial Plate Double Sound Plate Mouth Call. Primos Hunting Calls.