This variable resistance box is very easy and simple to operate, giving you huge convenience. The variable resistance box can be used for physics electricity experiment. The teaching variable resistance box is simple and delicate, excellent and reliable, carefully crafted. Features -Color: Black. -Material: Plastic. -Size: About 14.00X10.00X5.00cm/5.50X3.93X1.97in. - Made by plastic material, safe and , which could be used for very long time. - It is a selection of professional variable resistance box, which has good stability and high accuracy. - Great instrument for learning physical and electrical experiments, easy to operate. - The contacts resistance is stable and reliable when the resistance box is properly used to rotate each group of knobs. - The variable resistance box teaching instrument is suitable and wonderful for school, laboratory use. Package list: 1 x Variable Resistance Box