The GRAND PITSTOP Skull Cap for bikers is likely a product designed to be worn under a helmet for added comfort and protection while riding motorcycles. The term "skull cap" suggests it is a close-fitting cap designed to cover the top of the head. The black color is common for such products, as it tends to blend well with motorcycle gear. These types of skull caps are often made from moisture-wicking materials to keep the rider's head dry and comfortable during long rides. They may also provide some degree of insulation to help regulate temperature. Additionally, they can help to absorb sweat and prevent it from dripping into the eyes, which can be particularly important for safety and comfort during hot weather or intense rides. Overall, a skull cap like this can be a practical accessory for bikers, offering both comfort and functionality while riding.