I work out in the community and always take my shaker with me, I fill up with ice cold water before I start and its always cold when I am ready for my shake. before they came out I always had tetras but now I can vary my flavours more.
Lakeland do one that has a wire ball inside (same as the W8 blendi bottles) they are fab! no lumps guaranteed not sure how much but mine from W8 was £6.95 I think... I love it, a lot easier than a blender.
Now I have tried both Tetra's (thought choc was bad but banana was evilly bad, yuck) I am pretty sure that my shaker will be making day trips with me lol!