| Alias | Gelignite |
| Birth | 07/11/1991 |
| Age | 31 |
| Debut | 13/04/2012 |
| Stance | Orthodox |
| Height | 175 cm |
| Reach | 181 cm |
| Residence | Cronulla, NSW |
| Birthplace | Darkes Forrest, NSW |
| Nationality | Australian |
Jack ‘Gelignite’ Brubaker (born November 11, 1991) took up boxing after being attacked by two men on his way home from work who mistook him for someone else. After the scary incident, Brubaker was determined to learn how to defend himself and joined South Side Boxing where he began learning the boxing basics and rapidly excelled.
On the eve of Brubaker’s 18th birthday, he had his first amateur fight, which he won via technical knockout. After the initial win, he was hooked and continued to fight, winning state titles and eventually turning professional at the age of 20.
Balancing full time work while studying for his plumbing license, training and participating in his first nine professional fights became impossible too much for the orthodox boxer who gave up his day job to pursue his goal of becoming a world champ.
