They are LED's, so if you use them without the light hubs, then you will need to add appropriately sized resistors. Otherwise you will burn them out if your supplies are greater than around 3V. The big advantage of the light hubs is that they work like variable resistors so you can just plug it in and adjust to your liking although obviously more expensive than plain resistors. Any good electronics shop should be able to help you find the right sizes or you can probably just do an internet search for a simple calculator.