Gel in general (including mousepads and wristrests). There was a time in the late 90's when "real" gel was made. It is almost impossible to find nowadays.
My family owns 2 vintage mousepads (filthy but better than anything you can buy nowadays). One belkin, one fellowes.
I myself own 1 perfect vintage belkin mousepad, and 2 damaged vintage belkin mousepads. I also own 1 perfect vintage fellowes wristrest.
These things are nearly impossible to differentiate from the pictures on ebay. Take for example - the top one is my 1 perfect vintage belkin mousepad, while the botton one is a different variation that looks nearly identical. The top one is heaven, while the bottom one is **** (hell is reserved for different variations than this one).

