Base sizes are as follows for F&F 25mm:
Inf 2" wide x 1.5" deep, (3 to 5 figs per stand). Cav 2" wide x 2.25" deep, (2 mounted figs). Art 2" wide x 3" deep, (1 gun).
Div Command 2" wide x 2.25" deep (1 mounted fig), and Corps command, 3" x 3" (3 comm figs)
Dismounted cav, 2" wide x 1.5" deep, (2 figs).

Hope that helps, Dave