This is a mini 2-wire voltage meter that can be used to measure any DC voltage than ranges from 2.5 to 30 V. The RED wire is connected to postive, and black is connected to negative.         

This is a mini AC power meter that can be used to measure the power efficiency of appliance.  Specification: Voltage: AC85-250V Measured power: AC 0.0 - 99.9W - 250W Resolution: 0.1W (< 100W), and 1W (> 100W) Current: <...

These alligator clips are useful  for smaller wires that you don't want to deform. The clip has smooth  flat metal blades that clamp down on the wire, making for a good  connection to thinner wires. There are strain relief crimp points and...

This is a 9V battery snap with barrel connector, works perfectly to add a 9V battery to your Arduino USB board. Center-positive 5.5x2.1mm barrel connector.