Fernando 4 As other buyers says, the white boards are a bit bended, the different size boards do not snap with each other, some holes aren't open, the prints are not good (weak and faded), the + and - rails sometimes do not match, and the metal contacts do not always match with the plastic holes and you will have to try many times to connect the leads of the components.But these are everything minor concerns. The important ones are: 1-the good price and 2-they are very useful.