ASUS A42-U31 Battery Fit With Following Models:

 

ASUS U31 Series(All)

ASUS U31E U31F U31J U31JC U31JF U31JG U31S U31SD

ASUS U41 Series(All)

ASUS U41E U41F U41J U41JC U41JF U41JG U41S U41SD

ASUS P31 Series(All)

ASUS P31F P31J P31JC P31JG P31S P31SD

ASUS P41 Series(All)

ASUS P41F P41J P41JC P41JG P41S P41SV