We test several values of the surface area exposed to different probe sizes (1.2 Å, 1.8 Å and 2.0 Å). The probe occupiable volume is chosen to measure the void fraction (VF) for different adsorbent by using probe sizes of 1.8 Å (close to the radius of krypton) and 2.0 Å (close to that of xenon). This definition of pore volume demonstrates a better agreement with experimental nitrogen isotherms. Given the objective of predicting the difference between low-pressure selectivity and ambient-pressure selectivity (for a specific gas mixture composition), some descriptors hold little importance, and the key factor lies in the difference in accessible volume and affinity of the remaining pore volume with xenon compared to krypton. The intuition developed in the previous study outlines the role of a diverse distribution of pores with different xenon affinities. We test different combinations of geometrical descriptors (along with the following energy and pore size distribution descriptors) using a cross-validation scheme on the training data. Using these accuracy results, from all the "standard" descriptors mentioned in the literature, the following 7 descriptors are retained: C%, N%, O%, LCD ("D_i_vdw_uff298"), PLD ("D_f_vdw_uff298"), SA for a 1.2 Å probe ("ASA_m2/cm3_1.2") and VF for a 2.0 Å probe ("PO_VF_2.0"). Additionally, we introduce a new descriptor ∆VF to represent the difference in void fraction values, specifically the difference in volumes occupiable by xenon (2.0 Å) and krypton (1.8 Å). A comprehensive presentation of all these descriptors, including other geometrical descriptors based on pore size distribution, can be found in Table .