I use grade 25 on most everything, grade 10 on parts with ground races, such as Campagnolo, Dura Ace, Higher end Suntour. To each his own. The grade is a quality and measurement of roundness. The lower number, the higher standard the ball is made. Using Ceramic, balls can be made to very higher tolerances. But there is a draw back, they have to be serviced more often. Again you can use what you want, this is how I do it for me.