There are two types of length that Single and Double.
Only Ozak has linear bearings series with Oil Hole.
It has oil holes on surface of the outer bush, and it can obtain a stable long term life because all balls is filled in the grease or oil by providing the oil supply holes to the housing.

Standard(Straight)Flanged Single TypeFlanged Double TypeFlanged Long TypeFlanged Al HousingAl Housing
Cast Iron Linear HousingLinear Units