I want to buy servomotors that can move a cylinder with a inertia of 0,688 Kg-m2, the friction is minimum. That's mean sevomotor with a inertia greater than 0,0688 Kg-m2.

 

There are lots but instead of moment of inertia, you should specify nominal torque.

 

There are many factors to include when selecting your servo motor. Depending on the motion profile you need (accel/decel rate and velocity) and the accuracy you need to achive, you will not only want to watch your inertia mismatch, but also the peak torque and velocity of the servo. You may also wish to incorporate a servo quality
gear reducer to minimize your servo size and magnify your feedback resolution. Basically, you need to supply more information. Try locating some free sizing software from companys such as Allen-Bradley (Rockwell).