Circuit-Test Solderless Breadboards allow you to easily assemble and test circuits without the use of solder, providing you with a quick and reliable method of prototyping. This is an advanced version of the "half size breadboard" (MB-400) with more tie points and a removable jumper on distribution strip allowing selection of different voltage. Electrical connection is made by inserting your component lead through the 0.1" spaced holes to the spring clips mounted on metal strips within the ABS plastic board. These strips provide a common electrical connection so additional components can easily be added. Breadboard rows and columns are numbered and lettered to assist in component placement and polarities marked on the power rail.