. Hydro Flask - Standard Mouth Flex Straw Cap. Color Black. Low Stock. $14.95. 4.5 out of 5 starsBest SellerAdd to favorites. 0 people have favorited thisLow StockBrand NameHydro FlaskProduct NameStandard Mouth Flex Straw CapColorBlackPrice$14.95Rating4Rated 4 stars out of 5(210)