Includes 3 easy-to-use attachment points, plus a cinch systemfor secure fit; bright yellow gives daytime visibility andreflectivity for low light. S/M fits Blowfish, H.A.W.G.,Cloud Walker, Trail Blazer, Day Star, & other packs between1000 and 1700 cu. in. M/L fits Runner, Alpine Explorer, andother packs between 1700 and 2300 cu. in.