# Installing a pre-drilled thumb insert

1. For pre-drilled or pre-molded thumb inserts, select "Round" for Hole Type.
2. If installing a Contour or Turbo pre-sized insert, find the right size insert to fit the sides of the thumb comfortably.
3. Click "Size" to open the Drop-down list: [![image.png](https://wiki.spectrebowling.com/uploads/images/gallery/2025-05/scaled-1680-/aF9image.png)](https://wiki.spectrebowling.com/uploads/images/gallery/2025-05/aF9image.png)
    
    [![image.png](https://wiki.spectrebowling.com/uploads/images/gallery/2025-05/scaled-1680-/G24image.png)](https://wiki.spectrebowling.com/uploads/images/gallery/2025-05/G24image.png)
    
    [ ![image.png](https://wiki.spectrebowling.com/uploads/images/gallery/2025-05/scaled-1680-/hs0image.png)](https://wiki.spectrebowling.com/uploads/images/gallery/2025-05/hs0image.png)
4. When you select the correct size, it will appear in the "Size" box
5. Then click on the "Insert OD" button to open the Drop-down list for the bit size.[![image.png](https://wiki.spectrebowling.com/uploads/images/gallery/2025-05/scaled-1680-/wN2image.png)](https://wiki.spectrebowling.com/uploads/images/gallery/2025-05/wN2image.png)
6. Select the drill bit size for the correct OD of the insert:
7. [![image.png](https://wiki.spectrebowling.com/uploads/images/gallery/2025-05/scaled-1680-/zB0image.png)](https://wiki.spectrebowling.com/uploads/images/gallery/2025-05/zB0image.png)
    
    [![image.png](https://wiki.spectrebowling.com/uploads/images/gallery/2025-05/scaled-1680-/GEjimage.png)](https://wiki.spectrebowling.com/uploads/images/gallery/2025-05/GEjimage.png)
8. You can then select the Brand/type of insert by clicking in "Insert type"  
    
    1. Turbo Xcel Round / Oval
    2. Contour Round Taper / Oval Thumb Sleeve
    3. Example: [![image.png](https://wiki.spectrebowling.com/uploads/images/gallery/2025-05/scaled-1680-/qVyimage.png)](https://wiki.spectrebowling.com/uploads/images/gallery/2025-05/qVyimage.png)
        
        [![image.png](https://wiki.spectrebowling.com/uploads/images/gallery/2025-05/scaled-1680-/Kayimage.png)](https://wiki.spectrebowling.com/uploads/images/gallery/2025-05/Kayimage.png)
        
        [![image.png](https://wiki.spectrebowling.com/uploads/images/gallery/2025-05/scaled-1680-/j20image.png)](https://wiki.spectrebowling.com/uploads/images/gallery/2025-05/j20image.png)
    4. You are all set to drill the thumb !!!!
    5. The process is the same with the pre-sized oval sleeve thumb as the round thumb.
    6. Note: If you are using either a Turbo Xcel Oval or a Contour Oval thumb insert, you must align the oval to the proper angle for the bowler before you glue it in permanently.