The PT person recommended this one to me - moist heat and digital - you can set it for temp & time. I got the 14 x 27 size for more coverage.
14 x 14 is kind of small unless it is for a smaller area of use.
http://www.amazon.com/gp/product/B00...5214020&sr=1-1
Had it since 2005 and still works great.