One size fits all. Works on all hair types. For women and girls of all ages. 12 pieces in zippered pouch. They measure 2.5 inches long x .50 inches wide. . They hold more hair than regular small tipped bobby pins. They work well in buns, updos and French Twists making a perfectly straight line when inserted. They come in a re-usable zippered pouch for convenience and storage. Mia Sqhair Pins are square shaped bobby pins, hair pins that are great for thick and/or long hair.