This Thunderbolt icon is a responsive icon. This means that it's optimized for four resolutions, from tiny 16x16 until highly detailed 80x80. The style comes from the latest Microsoft Office, which makes it perfect for any Windows applications, in particular, those with ribbon toolbar control. Unlike other icon packs that have merely hundreds of icons, this monster icon pack contains 15,300 icons, all in the same style and quality.
The icon is a logo of Thunderbolt. The icon has a bunker like shape, with what appears to be a long horizontal rectangular window in the center. There is also a lighting bolt with an arrow on the bottom of it, located directly on top of the bunker shaped object.