this kind of claim is not acceptable.
Even if we can understand that the insulator has a metal flange slightly different from the insulators of the previous supply (no. two drain holes instead of four), please understand that this is really a small visual detail and, of course, technically there is not any problem (it is 100% equivalent).
We do not have any element to claim this insulator to our supplier because there is not any technical reason to do it and so the supplier cannot replace it.
Please explain this to the customer in order to settle the problem.
If the customer insists on the replacement of this insulator, we will send a quotation for this.
Waiting your news, we remain,
Yours faithfully,