Natick Labs developed the ERDL camouflage boonie hat in 1968 in response to a request from Army Material Command. Officially called the Type II Jungle Hat, it was made from Quarpel (Quartermaster developed water repellent) treated 6-ounce rip-stop cotton poplin fabric. The design of the hat was almost identical to the standard OG-107 boonie, except that it boasted a wider brim (3-inch vs. 2½ -inch) for added protection against sun and rain.1
1. Support To United States Army In Vietnam - Clothing & Organic Materials Vol II (United States Army Material Command Aug 1968)