Oversized Half-Gallon Stainless Steel Jumbo Flask – 64oz $12.99 Free Shipping.  Keep your next drink handy at all times with this Oversized Half-Gallon Stainless Steel Jumbo Flask. With a sleek and sturdy stainless steel design and a tight-fitting screw-on cap, this flask can be used to safely transport up to half a gallon of your favorite spirit!