"Silnylon" is a ripstop nylon that's been impregnated with silicon. Silnylon is popular for making ultralight backpacking gear and high performance parachutes because it is:
100% waterproof
Impermeable to air flow
Strong & durable
Ultralight & compact
FotoSharp's camera rain covers are made from silnylon that weighs ~1.3 oz per square yard. White silnylon is semi-transparent (see photos below), which allows you to read the print on the camera's controls when the fabric is held against the camera. You can also shoot a TTL flash thru our white silnylon covers.