What does the structure of exoKuiper belts tell us about planetesimal formation?

ExoKuiper belts are a common component of planetary systems that occupy their cold outer regions and whose dust is readily detectable in around 20% of stars. This makes these belts ideal objects to probe those outer regions whereplanet surveys have struggled to detect all but the most massive exoplanets. The dust in exoKuiper belts is not simply a leftover from protoplanetary discs, it rather is a product of collisions of much larger planetesimals.These belts thus offer a unique window to study the formation and evolution of planetesimal discs as the distribution of dust encodes the planetesimal formation history of these systems. Over the last 10 years, ALMA dust observations have transformed our understanding of exoKuiper belts by constraining their morphology. This has revealed a great diversity in terms of belt radii and widths. The ongoing ALMA large program ARKS is constraining the detailed structure of these discs for the first time. In this talk, I will give an overview of theresults of this program, with a specific emphasis on the radial structure of these discs. Preliminary results show a wide diversity of substructures, some of which resemble the multi-ring structures in protoplanetary discs. This comparisonbetween the substructures in exoKuiper belts with those in protoplanetary discscan tell us where planetesimal formation is most efficient in protoplanetary discs.