I know the majority of guys on this forum say B118, but you really should go by soil type and to some extent winter hardiness depending on where you are located. B118 can be too vigorous on good soil, it is recommended for weak soil, spur type varities of apples or replant situations. Depending on your situation you might give MM106 a look if your looking for a semi-dwarf tree. My grafts did outstanding on MM106 this year. The oldhome x pear rootstocks are resistant to fireblight. I highly recommend Cummins for them, most of my pear rootsock from Century Farms did not survive, vey poor root development on the rootstock.