improves strength in waist. Plastic + steel ball+ magnet, diamention:29x4cm, net weight: gift box di improves strength in waist.Plastic + steel ball+ magnet,diamention:29x4cm, net weight:gift box dimensions:30x30x4.5cmqty/ctn:15pcscarton dimensions:63*31*31.5cmN.W./G.W.:13kgs/15kgs. 29cm magnet twist board