we produce some QC tools, they are used to check some  parts , Machin etc.  plug gauge , ring  gauge, lamp cap gauge, lampholder gauge  are normally used checking size , we produce these thread gauges for many years. we also provide many standar about thread gauge and lamp gauge, such as spain-UNE 20315/IEC 60309, germany-DIN 49440, French- NFC 61314，England- BS 1363， America- UL 498 and so on.