In a grease composition which essentially comprises a base oil and a thickener, a mixture of a urea compound and lithium soap is blended as the thickener. In a front half of a housing, a chucking zone is located in a widthwise center. Each element of a first element type is associated with a baseline value, the baseline value being constant throughout a respective assigned time interval. 5-fold increase in total cells, an 6. The inter metal dielectric layer is characterized by a second thickness.