Ronan McLaughlin, last year's winner
Around 300 riders will take part in the second staging of the Donegal Atlantic Way Ultra 555km Cycle which gets underway in Letterkenny on Friday morning.
The first of the 31 solo riders will roll off the ramp at the Mount Errigal Hotel at 10 am, with the other 30 heading off at one minute intervals thereafter.
After a 20 minute break, the 20 two-person teams will set off at 10.50 am.
There are 37 four-person teams and the first of those head out at 11.30. The eleven eight-person teams are the last group to take the countdown. The first team roll away at 12.30 pm, with the last off off at 12.40 pm.
Last year's winner, Ronan McLaughlin, who rode the An Post Rás in May and followed it up with victory in the Gran Fondo Giro d'Italia Northern Ireland - it had a field of 4,631 riders - earlier this month, is back to defend his title. Ultra cyclist specialist, Joe Barr, who was third last year, is also back to give it another go.
A former winner of the Race Around Ireland, he was third overall and first over-50 in the Race Across Italy earlier this year.
Other notable solo riders include Adrian Callaghan who is reigning national triathlon middle distance champion, winner of The Race 2017, Marty Lynch, and Matthew McKinley, who won the two-person team event last year along with Conor McElwaine - their time was 17 hours and 45 minutes.
Ronan McLaughlin's winning time last year was 19 hours and 45 minutes, while the first of the four-member teams was Tir Chonaill GAP Cycling Club in 20 hours and one minute.
The time allowance for all categories is 40 hours.
For more log on to https://donegalatlanticwayultra.com/