The Practi-CRM Compression Rate Monitor is designed to measure compression rate when practicing chest compressions on a manikin. Worn on the student's wrist, a diode illuminates red when compressions are less than 100 per minute. When compression rate rises to 100 cpm or higher the diode illuminates green. Flexible wrist band fits any size wrist. May be used with any training manikin. Comes with a 1 year warranty. Sold individually or in packs of 4.