Dear Alessio,
(I changed the Subject line so that other people may be able to find this answer later.)

Unfortunately there is no specific option for arrow-tip width.   Probably you have already been looking at the options of the "cartoon style" command:
<https://rbvi.ucsf.edu/chimerax/docs/user/commands/cartoon.html#style>

To minimize the difference between the arrow tip and coil segment, the only choices I can see are to use a smaller "arrowScale" value, although that will decrease the width of the whole arrowhead, not just the tip.  For example,

cartoon style arrowScale 1.5

Another issue is that the arrow tip is still an oval rather than circular cross-section like the coil. To get it closer to a circle requires increasing the fineness of triangulations along the ribbon path with the "divisions" value, for example

cartoon style divisions 40

Using higher values increases number of triangles drawn and may slow responsiveness of the program.  Cartoon style won't let you use >40, but if you want an even higher number you can use a different command to do it, for example

graphics quality ribbonDivisions 100

<https://rbvi.ucsf.edu/chimerax/docs/user/commands/graphics.html#quality>

I hope this helps,
Elaine
-----
Elaine C. Meng, Ph.D.                       
UCSF Chimera(X) team
Resource for Biocomputing, Visualization, and Informatics
Department of Pharmaceutical Chemistry
University of California, San Francisco


> On Aug 28, 2024, at 1:25 PM, Alessio Nocentini via ChimeraX-users <chimerax-users@cgl.ucsf.edu> wrote:
>
> Dear Elaine, sorry for asking again for your support, but I am having problems in passing from Chimera to ChimeraX.
> Although I checked thoroughly the guidelines, I did not find how to reduce the size of the Arrow Tips (as they were called in Chimera, ribbon style editor panel), to fit the size of the coil.
> Here you have my case.
>
> Thank you a lot
> Best
>
> Alessio
>
> <image.png>
>
> I