Bubble size distribution at x_H II ∼ 1% using the same parameters (inferred with the model using Sheth & Tormen 1999) in Eq. (11) using the CMF of Eq. (2) based on Sheth & Tormen (1999, green line) and the CMF of Eq. (3) based on Press & Schechter (1974, purple line). The Numerical BSD from the HIRRAH-21 simulation and a numerical fit of the reference BSD using Eq. (1) from Furlanetto et al. (2004) inferring the efficiency parameter ζ (yellow line) are shown for comparison.