Double Pendulam

This is a double pendulam.
You will need.

2 x M4(25mm) Nut
8x M3(15mm) Nut
8x M3 Bolt
2x Ball bearing(4x13x5mm: http://www.banggood.com/10pcs4x13x5mm-Miniature-Metal-Sealed-Metric-Radial-Ball-Bearing-624-ZZ-p-79910.html)
5x 8mm Steel Rod(I paint them Black for contrast)