Type A - without knurling
Type B - with knurling
GN676.1 Push Pull Knob, Concave Top, Steel, With or Without Knurling
These push/pull knobs are used in applications where a push or pull movement is required. Their concave top gives a more comfortable thumb grip, and knurling makes the grip more secure.
The knurled model (Type B) can be used as an attractively shaped knurled knob with a threaded blind hole.