Kwa hiyo criterion zilizo tumika hapa ni ability to create and sustain an erection, sio?
Ila kuna categorization inayo tegemea uwezo wa kukaa for long before ejaculation, kuna ambao unategemea ujuzi wa preliminaries, mngine wa ability to 'deliver' in different positions, ingine ya ukubwa/udogo wa uume (
Boflo alianza hii leo jukwaa la wakubwa), kuna inayo tgemea creativity and innovation skills (hapa ndio wale wa
Kongosho na
Preta wanakuja) etc.
I think that the best researches ni zile zinazo combine two or more of these criterion. sasa itakua hujwawatendea haki wanaume if you reduce them to just 4 categories, each of them has his own level of 'performance' based on a combination of many criterion and his sexual partner preferences.