New Design! Darcy Duck Tub Tester Card is a stock-designed tub temperature tester with a stock temperature strip. Use this card in combination with the elbow test. This item hangs on the bathroom doorknob or tub spout, so it is close and available at all times. No batteries or power are required. The thermo strip detects the temperature, and there are three easy-to-use temperature ranges. It is great for at-home use, pediatricians, preschools, midwives, hospitals, and daycare facilities.