XGeology Double Right Angle Prism<div style="text-align: left;"><strong>[Product Information]</strong><br><ul><li>The Double Right-Angle Prism 90 : http://www.pobonline.com/articles/89550-back-to-basics</li><li>Fig. 26 A double prismatic square : http://www.fao.org/docrep/R7021E/r7021e05.htm#4.3.2 the double prismatic square</li></ul></div><img src="http://ecx.images-amazon.com/images/I/412kvtDdyaL.jpg" noproxy><img src="http://ecx.images-amazon.com/images/I/31fFcr7BPNL.jpg" noproxy><img src="http://ecx.images-amazon.com/images/I/21QZ4DzJxiL.jpg" noproxy><img src="http://ecx.images-amazon.com/images/I/31ie4CW0WcL.jpg" noproxy><img src="http://ecx.images-amazon.com/images/I/21KIet50c1L.jpg" noproxy><img src="http://ecx.images-amazon.com/images/I/31I3w6zi2JL.jpg" noproxy><img src="http://ecx.images-amazon.com/images/I/41TLZ4esVAL.jpg" noproxy>