does anyone have an opinion on future cue tips?

I am considering purchasing a future cue tip. Does anyone have any experience with these composition tips, if so I would appreciate any feedback on their performance.

Also, the tips are available in sizes of 13, and 13.5mm... I use a 12 3/4mm tip right now. Will the composition tip be difficult to trim down to size?(I intend on taking to the dealer where I purchased my cue, so he will be the one doing the dirty work.)

[Scott Lee]

I was given some of these tips to try out a few years ago. Purportedly you didn't need to chalk using these "rubber" tips. They did hit the ball well, but I could not get them to stay on the cue...they kept popping off, regardless of what kind of glue I used. Don't know about trimming them down to odd-size shafts.

Scott ~ likes leather tips best