The first Dell Optiplex to use the BTX cases only was the Dell Optiplex GX520 & GX620 in 2005 and the last Dell Optiplex to use the BTX cases was the Dell Optiplex 780 in late 2009 (excluding Dell Optiplex 780 Ultra Small Form Factor, which used the Series 4 USFF case) the case shared many similarities to a similar BTX style Dimension line of.