a wool one could do that too!!!
i have a £30 stable rug to go under my mares rug, can't remember the make but it's good, good fit doesn't rub which is essential as my horse it very high withered, and my weave one does rub her too!! leaving white patches and sores.
if you want to know that make i can find out!! it's not very thick though about 200 grms!