For field events, including football, rugby, athletics, horse racing and motor racing etc, you require sufficient magnification to see the detail but a wide angle of view is also important, a magnification of 7x to 10x is an excellent choice for these applications.

If the binocular/ monocular is going to be exposed to the elements then a waterproof model is worth serious consideration, if the optics are likely to receive knocks, consider a rubber armoured model.

For daylight use select a compact model with a 25,26,32 or 34 mm objective, these will be ideal, if you are planning to use the binoculars in lower light you could consider a larger objective lens, for instance 42 or 50 mm.