SIG's .38 Spl. 125-grain FMJ features a flat-nose, copper-jacketed lead wadcutter bullet in a brass case. As with all SIG ammo, it features a clean-burning powder to reduce fouling (important in those .357 Mag. revolvers when firing .38 Spl.).
Currently only the 125-grain bullet weight is offered in both FMJ and V-CROWN guise, but if SIG's track record is any indication other bullet weights may join this initial offering. There's currently no word on whether or not a +P version will join the offerings.