1. Zirconia flap disc, with fiberglass backing pad
Size        Arbor GRIT            MAX RPM  Type
4" 5/8"     36# 40# 60# 80# 120#  15300    T27 & T29
4-1/2" 7/8"                       13300    T27 & T29
5" 7/8"                           12000    T27 & T29
7" 7/8"                           8600     T27 & T29

2. Aluminum Oxide flap disc, with fiberglass backing pad
Size        Arbor GRIT               MAX RPM  Type
4" 5/8"     36# 40# 60# 80# 100#120# 15300    T27 & T29
4-1/2" 7/8"                          13300    T27 & T29
5" 7/8"                              12000    T27 & T29
7" 7/8"                              8600     T27 & T29

T-27/Flat - Used when grinding on flat surface, correct angle recommended between 0-15 degrees, best choice for smooth finishing.

T-29/Conical - Built in angle for grinding, this design is excellent for contour and edge work, angle at 10 degrees. It also provides greater surface contact and is more aggressive. Best at more dramatic angle of 15-25 degrees.