Primary use of these foam mandrels is for sanding organic shapes - especially concave ones which are difficult to sand with standard sanding tools mostly made to handle best flat surfaces. You may use these mandrels with batery powered drill, but I would reccomend an angle drill. 

PowerCarving foam bowl sander set includes:

1x FREE hard 50 mm EVA foam mandrel
1x FREE medium 50 mm EVA foam mandrel
1x FREE hard 75 mm EVA foam mandrel
1x medium 50 mm EVA foam mandrel
1x medium 75 mm EVA foam mandrel
1x soft 50 mm EVA foam mandrel
25 pcs of 50 mm sandpaper discs in various granulations
25 pcs of 50 mm wavy sandpaper discs in various granulations
3 pcs of 75 mm sandpaper discs