We describe “off-the-shelf” capillary microfluidic devices for droplet fission. The cheap and simple commercial capillary adapters are characterized by perfect sealing, easy assembly and convenient cleaning. Primary droplets, bigger than 65 μm, without being plugs, can be split into uniform daughter droplets (15–170 μm) to obtain smaller droplets and increase their concentration. The relative size of daughter droplets can be easily controlled by adjusting the length of the glass capillary tube.