here's some pics of the different brands:

http://www.mustangdyne.com/products/MD-600/600-series.gifhttp://www.panhandleperformance.com/images/dyno1.jpg

http://www.dynojet.com/automotive_dyno/224xLC_dyno/images/224xlc_1.jpg

http://www.superflow.com/autodyn/sf-790webnew.gif