It seems like you're looking for information about a double chabi (also known as a double-ended key or a double-sided key) with two different key blade sizes: 27mm and 30mm. Double chabis are typically used for locking and unlocking certain types of locks. The specific dimensions you mentioned (27mm and 30mm) likely refer to the width of the key blades at their widest points.
The two different sizes may be designed for use with different types of locks or for specific security applications. It's important to note that the precise specifications and terminology can vary depending on the manufacturer and the region, so it's always a good idea to consult the manufacturer's documentation or a locksmith for specific details about a particular double chabi.
