No inner or outer wall with wall cylindrical roller bearings
NU-cylindrical roller bearings, its outer wall with two on, and no inner wall.
N-type cylindrical roller bearings, at two of its inner wall, and no outer wall.
NU and the N-type cylindrical roller bearings, in a certain range relative to the bearing axis to allow me to make axial displacement of two-way, that could take the shaft caused by thermal expansion changes in the length, as it applies to non-bearing position. To be capable of sustaining their large radial load, but can not afford to axial loading.