Question is a bit vague, but it probably has to do with the braking characteristics of fixies. A common way of braking a fixie is by making the rear wheel skid. Getting the skid is easisest when you have the cranks more or less horizontal, and may people prefer a certain foot forward as well. This means that the wheel will lock up in a limited no of positions, and in these places the tire develops skid patches. By stuffing something into the tire as a liner on these places one can avoid flats and increase the useful life of the tire.
Considering that a fixie hub can be built into any size rim, you can have a fixie in any size - as long as you're ready to pay for having a wheel built.
The cast of Fixie Dave - 2008 includes: Dave Nice as himself
Fixie Dave - 2008 was released on: USA: 30 April 2008 (festival premiere)
Micargi
trendland.net/2009/02/26/most-expensive-fixie-in-the-world/ this is it it think its about $110,000, gold plated with diamonds etc
One can purchase a Fixie bike from Walmart for as little as $100. They can also be purchased from both Amazon and Ebay or in the UK one can buy from Halfords.
Fixie bike are bikes (usually road bike frames) that have a fixed rear sprocket which allows you to pedal forward like normal, but does not allow you to just coast . If you pedal backwards it goes backwards if you pedal slow it will remain slow. The whole point of a fixie is to eliminate brakes shifters to simplify a road bike.
http://mashafix.com/mashafix-for-tth13tth/Its a brand for fixie kids.
Ebay, craigslist, yard sales.
52cm at best;)
Any bike can be turned into a fixie, at varying degrees of difficulty. But if the rear wheel can be moved back & forth to adjust chain tension it'll be so much easier.