Is there any way to specify the size of an arrowhead in printer's points? I'm looking for something that would have similar functionality to `AbsolutePointSize`, `AbsoluteThickness`, or `AbsoluteDashing`, except for Arrowheads.

The best I have come up with is to use something like `Arrowheads[1.5/???]`, where `???` is the width of the `Graphics` object. However, this doesn't work if I don't know the width of the graphic. I've played around with using `Offset` or `Scaled`, but I haven't been able to get them to work for this purpose.

**Edit:** Thanks for the suggestions so far. A few comments:

1. So far I have been using `ImageSize` combined with the `Arrowheads[1.5/???]`, but this is annoying for two reasons. First, it makes it impossible to set the height of the graphic using `ImageSize -> {{10000},{hmax}}`. Second, it means that I have to pass the ImageSize as a parameter through a series of functions that I have written.
2. The sizes `Tiny`, `Small`, `Medium`, and `Large` are exactly what I'm looking for, except that they don't seem to work with custom arrowhead graphics. In particular, the specification

`Arrowheads[{{Medium, 1/2, 
Graphics[Line[{{-1, 1}, {1, 0}, {-1, -1}}]]}}]`

within a `Graphics` command followed by an `Arrow` produces the following mysterious error:

`Encountered "Graphics[Line[{{-1, 1}, {1, 0}, {-1, -1}}]]" where a Graphics was expected in the value of option Arrowheads.`

**Edit 2:** Problem solved! As Brett suggests below, it works to use offset coordinates:

```
    MyArrows = Arrowheads[{{0.000001, 0.5,
    Graphics[Line[{Offset[{-4.5, 5.4}], Offset[{4.5, 0}], Offset[{-4.5, -5.4}]}]]
    }}]

```

When using this approach, it seems to work better on curved lines to specify a very small arrowhead size such as 0.000001. Here is some sample output using the arrowhead style above:

![Sample picture](https://i.stack.imgur.com/w0m4Z.png)