E thirteen trs st chain guidethe trs trail security guide is designed to fill the expanding enduro and all mountain categories engineered to take extreme punishment dealt by riders on enduro bikes they are still light enough to use on xc specific bikes completely re designed for 2015 the trs guide offers the same world class chain retention in a lighter stiffer and far more adjustable design all polycarbonate parts are now solvent resistant so they wont get brittle or crack after exp