Grover Pro's innovative "combo" model was the first tambourine to use fully integrated German Silver and Phosphor Bronze alloys on one tambourine. Each pair of jingles consists of both silver and bronze alloys. The jingles are voiced in alternating patterns, guaranteeing harmonious resonance. A superb "go-to" instrument for those who want both highs and lows in one instrument. A padded case and Roll Ring™ are included with all Grover Pro headed tambourines!