The zafu is a round cushion that is used for Zazen. A medium-sized zafu is about 14 or 15 inches (38 cm) across.
It is possible to practice without a zafu, using a blanket folded several times, a rolled-up bedspread, or a couple of ordinary firm cushions placed one on top of the other.
To be isolated from the floor, it is better to place the zafu on a good carpet. The Japanese-style mat or zabuton is about 2 feet square and loosely packed with cotton or kapok to give a cushion effect for the legs. When traveling, It's possible to practice Zazen on the bed, provided it has a firm mattress, using a rolled-up blanket or pillows as a zafu.
Zazen needs the minimum of space; just enough space to sit with crossed legs.
Traditionally, Zazen is practiced facing a wall. Place the mat and zafu on the floor about 2.5 feet (90 cm) away from the wall.