170cc implants are less than half a can of CocaCola (360cc), and will add less than one cup size to whatever breast volume you started with. Of course, cup sizes vary significantly between bra manufacturers, so even these "guidelines" (about 250cc per cup) are generalizations, not specifics.
In addition, even the moderate profile 170cc implants are quite narrow, and may be less than ideal in "fitting" your breast base diameter and pockets. "Rock in a sock" is not a good look, so beware.
Most women who are afraid of "going too big" end up wishing they had gone larger, particularly when the chosen implants are so relatively tiny. See one or more ABPS-certified plastic surgeons for a second opinion or two before going ahead with surgery. This may save you a do-over operation! Best wishes! Dr. Tholen