The Trail is the quintessential size for the serious mountain biker, just enough space for two mountain tubes, multi-tool, patch kit, energy bar, and a couple of dollars. The entire front half of the Trail, top, bottom and sides are lined with 14 oz vinyl scrim to prevent wear points at the seat post or seat rails. Two top lash points allow adjustment to any seat and the quick release cinch strap is extra long to store bulky items below the bag. For on road night safety we also added a rear strobe loop. There's a zipped pocket on the bottom for your keys. Zippered expansion baffle increases bag's capacity by 25% Volume 58-79 cu in Dimensions 7 x 4 x 2.5-4, Extra long cinch strap for storing bulky items below the bag Top, front and sides are lined with 14 oz truck tarp vinyl for bombproof durability