Insulator manufacturers provide some electrical insulators, most of Insulator overseas manufacturers distributed in China or India to provide porcelain insulator and polymer insulator.

Should the insulators be supplied from overseas manufacturers, then it is mandatory that all conditions and inspections required by the corresponding agent be met and that all these costs be included in the tendered price. In particular, timber crates must be fumigated with methyl bromide with a concentration of 48 grams per cubic metre for 24 hours at 21 C. The supplier shall ensure that the procedure does not produce any deleterious effects to the insulators or the crates. 

Suppliers shall state:
(a) The period of service achieved by the items offered within tenders service conditions;
(b) Customers and overseas electricity supply authorities who have a service history of the items offered (including documented user service history, AND)
(c) Contact names and phone numbers of relevant employees of those supply authorities who can verify the service performance claimed.

In the absence of relevant insulator service performance, the information required in (a), (b) and (c) above shall be stated for service history in overseas countries. Priority shall be given to performance in environments similar to those described in Clause 4 above.

All Insulator manufacturers shall be done some insulator tests to ensure or enough the customers' requirements.