For the original DX3 I removed the stock foam, shaved the lip on the stock wheel leaving a little bit & pushed the TC wheel over top. It fit very snug so no glue required. Then I used the stock screw to secure the new steering unit to the radio.

On the M8 I removed the stock foam and slid the TC wheel over top. I had to use Shoe Goo to keep it in place. The screw was placed between the TC wheel & stock steering wheel so the whole unit could be secured to the radio.