the cup shaped one was first developed for a a thumb based handle we made for flight traffic controllers. In those days (1991) we thought a cup in a keyboard would be too big. Actually the new placement bellow not between the g and h key (long before it was a product) made the space for it... but we were to timid for the big style tops for years. the first ones were a chloroniated butyl that replace the awful protoypes that were slippery santoprene%$&$#,,,, but the very sticky butyl (that saved the product from sure death) were actually formulated by my father as the last consulting gig of his life... unfortunately they absorbed oil over a few months from fingers ... I tried everything and the bumpy one is nylon trying to mimic the amazingly gripy fish skin we found in Japan... the larger cup and domes of today are better still!

The cup ones last basically forever, the dotted one lasts not quite as long, and the fuzzy dome wears out in about 3 weeks.

I always thought there should be an aftermarket for designer Trackpoint caps, like Pink Hello Kitty Caps, or Black Spikey Hipster Caps, or Fleshy Famous Porn Star Caps.

I wonder if 3D printers can render the special kind of rubber that Ted's father designed for the trackpad tops?

I remember seeing purple ones at one point, and I don't think any manufacturer used that color as standard, so it must have been an option at some point.