Specifications:Product name:Smart key chainColor:black/blue/redProcess: 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 pocket2. Smart leader: Allows you to organize several units together.3. No noise: the keys no longer wobbles; avoiding metal noises.