Sapphire Setting Size: 4mm vs. 5mm Trillion Cut - Expert Advice

Question
I have a matched pair of pink sapphires, trillion cut 4.5mm can I use either the 4mm or 5mm setting and if so is it better to go small (4mm) or larger (5mm)?  Thanks

Answer
Greetings,
I'm not exactly sure what you're asking.
I'm assuming that you're talking about a bezel setting and in this case the wall thickness should be about 0.6mm, so you'd be wanting to use a setting that is close to 5.7mm.
Ordinarily a jeweller would make a setting to suit, but I assume that you're referring to a ready made sett.....
In any case I think I need some more information to fully understand what you are actually talking about.
Cheers and Thanks, P