Specifications: Product name:Smart key chain Color:black/blue/red Process: stamping + anodic oxidation. Material: A aluminum alloy is sandblasted and oxidized. 6061-t6 aviation aluminum. This is a compact and ultra-customized key solution. This product contains no metal noise and is used to organize and store key rings. In addition, this product is not limited to keys. As long as a user like it, you can integrate USB stick and RFID chip together. Size: Inner column diameter is 4mm. Please make sure your keyhole inside diameter is larger than 4mm. The standard inner column is about 11mm high (can hold 4-5 ordinary keys). If you have a special key, please measure it in advance. The cross keys can be installed (the thickness is equal to 3-4 ordinary keys). The vinyl head key can be installed, or it can be installed directly or electroplated to remove plastic supplement points. Description: 1. Compact design: Smaller than a pack of balls. Put it in your pocket 2. Smart leader: Allows you to organize several units together. 3. No noise: the keys no longer wobbles, avoiding metal noises.