Strong line-- Instead of cheap fishing line which other sellers used, our newton cradle use high quality nylon line which is strong enough to not be broken easily

SWING TIME--The balance balls continue in perpetual motion for only 15-20 seconds due to the resistance of the air and friction, but it won't influence the effect of playing although it can not reach the seamless convergence among balls in the vacuum.

PHYSICS EDUCATION TOY--It is a nice gift, we can send it to our friends, children, family.

APPLICATION--You can put it on your office desk or your home desk or on your shelf. It will be cool desk toy