Serotonin: Joy and Satisfaction Serotonin is known for promoting happiness, contentment, and tranquility. The bikes in the Serotonin series are designed to enhance your mood with every ride, featuring a sleek design and strong performance. These bicycles are ideal for anyone seeking a joyful urban riding experience, offering options ranging from single-speed to advanced Pinion gearing. PINION 1.9 Equipped with a sporty carbon fork, it delivers a dynamic and powerful riding experience for those who crave excitement.