What this means
The IEEE assigned the MA-L block 20C8B3 to SHENZHEN BUL-TECH CO.,LTD.. Every network interface they manufacture under this block has a MAC address beginning with these digits, followed by a unique per-device identifier. If a device on your network shows a MAC starting 20:C8:B3, it is SHENZHEN BUL-TECH CO.,LTD. hardware.