Their faces and bodies are covered in ink, telling the stories of the crimes they have committed and in honour of who they have done so all over their bodies.
They are drug pushers, murderers and weapons dealers - members of the Mara Salvatrucha (MS-13), a gang so feared in El Salvador that they have been left to run their own prison.
In Penas Ciudad Barrios, the Mara Salvatrucha control their own miniature society of some 2,500 incarcerated members, complete with a bakery, workshops, a hospital and rehab.
Marked for life: Two young members of the notorious Mara Salvatrucha gang show off their face tattoos in Penas Ciudad Barrios
The prison guards and the El Salvadorian army remain on the outside, ensuring that the prisoners stay behind bars, but doing very little to meddle in affairs on the other side of the gates.
Penas Ciudad Barrios is a maximum security prison exclusively housing Mara Salvatrucha gang members, located in the capital San Salvador.
In 2013, photographer Adam Hinton, from London, was granted access to the squalid gangland prison, originally built to house some 800 inmates, but now home to around 2,500 Mara Salvatrucha members, and the area of San Salvador populated by their families - Las Victorias.
‘The men stand around aimless with nothing to do except kill what seem like an infinity of minutes, hours and days,' Mr Hinton says.
'The vast majority of the inmates from the Barrios or slums. In El Salvador this is a place without hope or opportunity and the gang is the only real option. If the authorities catch you this is the place they literally dump you and forget about you - every inmate is made to feel just like that.’
Behind bars: Penas Ciudad Barrios is a maximum security prison exclusively housing Mara Salvatrucha gang members, located in the capital San Salvador, which is - in essence - run by the prisoners themselves
Run this town: In Penas Ciudad Barrios, the Mara Salvatrucha control their own miniature society of some 2,500 incarcerated members, complete with a bakery, workshops, a hospital and rehab
Roots: The Mara Salvatrucha was founded in Los Angeles area by El Salvadoran immigrants, and has since been brought back to their native country following repatriation
The violence between street gangs in the country is escalating, and last month, El Salvador saw the highest number of murders since its bloody 12-year civil war ended in 1992.
The National Forensics Institute (ILM) said there were 911 homicides in August, with 52 occurring on August 23, making it the deadliest month in nearly a quarter of a century.
From January to August, El Salvador recorded 4,246 homicides, an average of 17.5 a day, and up 67 percent on the
Feared: For years, the gang members have been left to run the prison, with the guards remaining on the outside
Danger: The violence between street gangs in El Salvador is escalating and last month saw the highest number of murders since in 1992
Violence has risen steadily in El Salvador since a 2012 truce between the country's two main gangs, the Mara Salvatrucha and its rival Barrio 18, began to fall apart last year. The truce had helped reduce the Central American nation's murder rate in mid-2013 to around five per day, a 10-year low.
The country's police estimates that 80 percent of the homicides are related to purges and score-settling between the country's gangs.
El Salvador is one of the most violent countries in the world, according to United Nations statistics, with a 2012 murder rate of 41.2 homicides per 100,000 inhabitants.
According to some more recent measures, El Salvador has this year overtaken Honduras, which had a 2012 murder rate of 90.4 murders per 100,000 people, as the country with the world's highest murder rate.
- MS-13 by Adam Hinton is published by Paul Belford ltd, £25