This is a simple, very common rectifier diode. Often used for reverse voltage protection, the 1N4007 is a standard for many power, DC to DC step up, and breadboard projects. 1N4007 is rated for up to 1A/1000V.
 
Specifications
Product name: Rectifier diode
Model: 1N4007
Forward continuous current: 1A
Forward voltage: 1V
Surge forward current : 50A
Max peak reverse voltage : 1000V
Reverse current : 5ua
Overall size : 2.5 x 50mm/0.1" x 2"(max,Dl)
Silver tone weight: 4g