Estimated ages and fractional widths (ΔR/R) for exo-Kuiper belts (circles), protoplanetary rings (squares), and the Kuiper belt (star). The belts with gaps around HD 92945, HD 107146, and HD 206893 are represented by ⊚ symbols. Ages and uncertainties for systems in the DSHARP survey were taken from Andrews et al. (2018). For systems in Taurus, we randomised their ages with a mean 2 Myr and a standard deviation of 0.5 Myr. For systems in Ophiuchus we assume use the ages reported by Cieza et al. (2021) and assume an age uncertainty of 0.4 dex.