Boosted Gear, also known as the Red Dragon Emperor’s Gauntlet, is a Sacred Gear wielded by Issei Hyoudou. Listed as one of the thirteen Longinus, it has the spirit of the Welsh Dragon, Ddraig, residing within it.
In the past, Ddraig fought against his arch-rival, the Vanishing Dragon, Albion, in a battle that was interrupted by the Angel's, Devil's, and Fallen Angel's who were at war during the time. In anger, both Dragons attacked the leaders of the Three Factions, which led to their bodies being destroyed and their souls being sealed into two separate Sacred Gear's, with Ddraig moving into the Boosted Gear, a Sacred Gear that eventually became one of the thirteen varieties of Longinus.
Boosted Gear takes the appearance of a red gauntlet with a green jewel and 2 golden spikes that manifests on the user's arm. In the anime, it's initial state looks like a regular Twice Critical. After a certain time, it transforms into a more Dragon-like gauntlet that covers up the user's hand and a majority of the arm.
From the Anime High School DxD
Update: Added DxdSepertate as additonal Obj that features 6 Obj files for each part (fingers 1-5 and a top part)