This is a fair three-sided die, with the special feature of clearly showing the value on a flat surface, face-up.
The roller is based on a Reuleaux triangle, with the corners slightly clipped to improve its rolling characteristics.
The numbers are sized such that the same amount of material is present in each face.
I believe that this roller form is superior to a cubic die with paired values, because an unscrupulous player able to throw a die such that it rotates on one axis can reduce their exposure to undesired values. (This is the case for all possible layouts of a d6, which stems from the fact that four is not divisible by three).
About this set
This metal form is a 1mm stainless steel shell with a hollow interior. Together with the rounded shape, this gives the dice a very pleasant feel and weight for rolling. They roll extremely well, and stop well centred on the faces. The ends have the round holes which gave this set of dice their name.
The digits are quite clear enough to view at a glance in plain stainless steel. Polished bronze steel is perhaps slightly less visible. If the numbers are not clear enough for you it is straightforward to enhance them by adding a small amount of a contrasting paint, then wiping off the excess.
Fairness testing details
I have tested this die for fairness by throwing it over 300 times.
I considered that the most stringent test for bias would be if the die was allowed to roll on its axis and stop unimpeded. Therefore I only counted successful rolls (and tried to make this decision before viewing the result to avoid experimenter bias affecting it).
I then performed a simple statistical test (chi-square). The result of this was : no evidence that the die is unfair. Statistical tests like this are annoying because you don't find out for definite that a die is fair. However, it should be good enough for most purposes.
I tested the previous version of this die in the same way. In that test, no bias was detected - but I did decide that the die didn't roll readily enough, hence the second version.