Convertors

Inches are the overall diameter of the converter. In general it is better to use a smaller diameter converter for higher stall speeds as their overall efficiency is better. In other words a 10 inch converter can be made to have a 4000 rpm stall speed but it's efficiency (expressed in a percentage) at higher rpm's is going to be poor, maybe 89% of true 1 to 1. Whereas if you used a 9 inch converter at 4000 rpm stall speed its efficiency would be closer to 97%.

One thing you have to take into account with converters is heat. The higher the stall speed the more heat it's going to generate.

In addition although you can pay a lot for a crappy converter, you won't get a great converter for little money. Stick with the bigger names and recommendations from people you trust. I personally will never buy anything else but a Turbo Action converter ever again. It was the best $1000 I ever spent.