Massage equipment will often go to the plastic ball and plastic ball, the size is basically in the 10mm to 25mm (BB, Airsoft, BBS) of the plastic ball material requirement is very high, because the plastic ball in direct contact with human skin, so the ball material must be non-toxic, usually use plastic ball massager mainly in the box in the foot massager, foot sliding on top, to ensure that the sliding (BB, Airsoft BBS), but not out, so massage plastic ball only 2/ exposed and foot contact, other 3/5 in the sleeve below, but also to ensure the smooth surface (plastic ball. BB, Airsoft BBS) will feel comfortable when sliding, so you can choose the material is POM plastic ball engineering plastics, commonly used is the treasure of M90-44, because the material treasure good polishing effect, High surface brightness, environmental safety.