A printing machine (Fig.4) of the type in which a latent image recorded on an image bearing surface (12) is developed with toner to form a visible image thereof, includes a development apparatus (52) for developing the latent image. The development apparatus (52) includes a housing (100) storing a supply of magnetically-attractable developer material containing toner. A moving flexible donor belt (112) mounted within the housing (100) spaced from the image bearing surface (12) transports developer to a development zone (136) adjacent the image bearing surface. A magnetic member (124) attracts and transports the developer material within the housing to the donor belt (112). A plurality of selectively-actuable electrodes (146) embedded within the donor belt are biased to create a powder-cloud of toner particles within the development zone (136). Within the development zone, the flexible donor belt (112) moves over a pair of spaced apart support rollers (148, 150) defining the width of the development nip. The spacing between the support rollers is adjustable to inexpensively create different widths for development nips from a common structure development unit, thereby saving image bearing member real estate within the development zone and improving the quality of image development.