Part No. Description Size mm Use 504-105 Sheave ball bearing 25 x 6 x 8 Ball block range 504-107 Sheave ball bearing 35 x 10 x 8 Main hal, heel & exit box 504-108 Sheave ball bearing 35 x 6 x 8 Heel, jib box 504-109 Sheave ball bearing 21 x 9 x 4 Heel 504-360 Plain sheave 21 x 4.2 x 9 Main hal, heel & exit box 504-361 Plain sheave 32 x 8.2 x 6 Heel, jib box