Pressure Pumpers -- For Investors -- The Bakken, North Dakota, USA

For investors, it might be interesting to know who manufactures the pressure pumpers used by Halliburton, et al, to fracture the Bakken wells (and the Haynesville, and the Marcellus, and the ... well, you get the picture).

I assume Cal-Frac Well Services and Weatherford are two of many, although they may also use pressure pumpers manufactured by others (Sundyne?). 

I don't know who makes pressure pumpers but at least one person has asked me the question, so I'm not the only one.

For a nice short review of the evolution of pressure pumpers, click here.

If there's enough companies, I might even be able to add a "top ten" list of pressure pump manufacturers to the sidebar at the right.