Constraints on the particle aerodynamic size (Stokes number τ_s) and turbulence intensity of the gas, where σ is identified as the root mean square turbulent gas velocity. The constraints follow from simulating the TNO size distribution (run turb-1p, black line), ALMA ring morphological analysis (blue lines; Rosotti 2023), and particle fragmentation velocity (orange lines; the adopted value for the Keplerian velocity v_K is the circular motion at 20 au). Under the assumption that the primordial belt featured conditions similar to ALMA rings, the degeneracy between τ_s and σ (or α_D; Equation (16)) can be lifted and we find, τ_s ~ 0.01, α_D ~ 10⁻³, and a fragmentation threshold of ~2 m s⁻¹.