09-404 Upper roller (symmetric)

Types of roller with removable silicone:
A: big head of roller, sealed bearing with steel balls
B: big head of roller, unsealed bearing with iron balls
C: sealed bearing with steel balls
D: unsealed bearing with iton balls

Types of roller with nonremovable silicone:
E: big head of roller, sealed bearing with steel balls
F: big head of roller, unsealed bearing with iron balls
G: sealed bearing with steel balls
H: unsealed bearing with iton balls