Factory installed parts grading:

WARNING: This page is about a different car, the 2004 Nissan Quest. However, it is still accessible from the selected car via links, so may be relevant.

Service parts apply only to grade 0.

Fig 1: Piston Grade Specification Chart
Courtesy of NISSAN MOTOR CO., U.S.A.

Fig 2: Applying Service Parts
Courtesy of NISSAN MOTOR CO., U.S.A.