Muslim women's head scarf lycra streachable under scarf.. Soft and comfortable.. Adjustable and stretch, easy to wear and convenient to put off Material lycra net. A hijab cap, also known as an undercap or ninja cap, is a head covering worn underneath the hijab by some Muslim women. It serves as a base for the hijab, helping to keep the hair in place and providing additional coverage. The hijab cap is typically made of stretchy and breathable fabric, such as cotton or jersey, to ensure comfort. It comes in various colors to match the wearer's preference or the color of the hijab being worn.