Kerr Cap Lining Requirements

[GAstiller01]

I've been trying to find the answer to this online for a while but have been unable to find a definitive answer. 

We are looking to start a line with 375ml glass bottles with a plastic kerr cap (most likely a 28mm) bottling a lower abv spirit (~12 - 17% ABV). Does anyone know what type of liner is required to be in the cap if any? 

I see unlined ones, EPE foam, PVC, etc out there as options but unsure what is the minimum required. I don't want to buy 5000 unlined ones and then find out we needed an EPE liner. 

Thanks.