Contents: 4 Pre-Filled Whitening Gel Syringes 0.4 fl oz (12 ml), 2 Comfy Tray Applicator Whitening Trays. Important: Read directions for proper use. As we continue to make great advances in oral care, sometimes we have to stop and enjoy a good laugh. Laughing releases endorphins, neurotransmitters that make you feel good. Exposing yourself to the laughter of others can have the same effect. At Rembrandt, we think laughing is essential to a healthy, happy mouth. After all, white teeth don't matter if there's nothing to smile about.