The rings are flexible soft metal with a coating of color. These rings feature a grooved inside, like a screw. Screw thread/Groove Micro Rings also known as Links or extend tubes Micro Links for used with stick shape/I-shape Pre Bonded extension hair. Cause each ring features a screw like groove on the inside, it provide the extra security and hold than other regular rings and tubes. These rings/tubes method is also attached with a needle and pliers, same step as when you use micro rings. It is so easy to close and easy to open. Needle and pliers are also available on request.