For Sale: 2015 Keystone Alpine 3900re Toy Hauler Fifth Wheel, Urban Loft Decor Toy Haulers / Sweetwater, Tx 2015 Keystone Rv Alpine 3900re Alpine Is The First New-generation Luxury Fifth Wheel. Designed For The Customer Who Demands A New Level Of Quality, Convenience, And Features Unimaginable Just A Few Years Ago. Alpine Was Engineered From The Frame Up To To Be A Generation Ahead Of Anything Else In The Market Today.