This set of nylon bristle valve guide brushes includes 5 popular sizes:
5/16" (7,93mm) x 2-1/2" (63,5mm) (GVP-1N)
11/32" (8,73mm) x 2-1/2" (63,5mm) (GVP-2N)
3/8" (9,52mm) x 2-1/2" (63,5mm) (GVP-3N)
7/16" (11,11mm) x 2-1/2" (63,5mm) (GVP-4N)
1/2" (12,70mm) x 2-1/2" (63,5mm) (GVP-5N)