We recently got two of these, as they seemt o be £15+ everywhere else at the moment and seem good value for money.
Info from the website:
Superior contoured support pillow.
Maintains your neck in an anatomically correct position for better support and overall pressure relief.
100% visco-elastic filling.
Size (L)48, (W)30, (H)10 down to 8cm.
Machine washable pillow cover