The difficult thing is the quality standard. Normally, 5A is close to perfect (some vendors describe as 6A 7A, which is Unreliable, 6A 7A may the top quality, and top quality pearl are waiting for their VIP)
In my opinion--4A is nice enough for most of fashion Jewelry making.
5A is very good quality
-no veins
-no fish bites
-no growth lines
-No milky, cloudy spots
-round…NO BUTTON
Very Perfect quality, 5A price, for sure is expensive