Twin bands: 

watch is always designers' one of favorite items to design, but most of time, the focus is on designing watch face and identifying the time, bands are usually "ignored". 

unlike most of watch bands , one side of band are different to another, Twin bands are completely identical to each other, we can use same tool to make one set of bands

 

2 bands are connected to watch with opposite direction , once they are connected with watch, 2 bands can lock each other with very quick action.