Need info on a stylus pen

[tommy2tone]

I noticed on the WC website I could get the rubber tips in different colors. My question is: Are there only certain pen(s) these can go on? I assume you just replace the fennel with the stylus?

 

[thewishman]

They fit 7mm tubes.

 

[bradh]

A word of warning on these tips. They work best when the metal is in contact with the user's skin. Don't make a closed end, one-piece stylus - it will not work well with an iPad or similar devices.