I took the 2 hour tour with my wife, but there were 4 people on the tour altogether including a young Irish couple who'd been picked up from the Blue Lagoon (returned at the end of the tour). The guide, Issac, was friendly and spoke excellent english.
The tour took in the lava fields and beaches around Grindavik, plus up and down one of the local "mountains" for an excellent view of Grindavik and the Blue Langoon.
The quad bikes are easy to ride, automatic gears and the throttle is activated with your right thumb, which I found easy but my wife complained about the strain towards the end of the tour.
The route taken covered a variety of terrain, some of which was vary bumpy and some requiring 4-wheel drive. The guide progressed as a reasonable pace, stopping regularly to ensure that everyone was OK, and with a couple of longer breaks to give peoples thumbs a rest.
The total tour actually took about 2.5 hours.
It was great fun, with some fantastic views and I strongly recommend this as an excellent way to spend half a day and see some more remote areas of Iceland.
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