Beech chips one of the substrates that can be used or added to dig boxes where the hamster can forge for food. Such boxes help mental stimulation making the hamster 'work' for their food rather than leaving their dried food in a bowl. (don't put wet/fresh food with it). They also like to dig in it just for fun sometimes.
 
Small 20x26cm, approximately 2 litres
Large 25x37cm, approximately 4 litres