I developed these to match the emerging forms of many mayflies and caddisflies. The sizes 10, 12, 14 & 16 are used primarily for trout all across the country. Size 12 & 14 in olive are great when the natural caddisflies hatch. The size 16 olive is my favorite when the beatis start hatching. The sizes 6, 8 & 10 are great for smallmouth bass matching the hexagenia, brown drake and caddis. Fish all of these across and downstream at a 20 degree angle with a slow six inch rod lifting action every five seconds.