1. Voltage matches. The TECHNOLOGY matches.
2. It mechanically fits and is pin compatible.
While NO ONE should write it will be OK, it might be.
I had a Toshiba Satellite M305D that is about 2 yrs old. I am now replacing it with a Toshiba Satellite M640. I had an extended battery for the M305D. The battery fits the new M640... the prongs line up, snaps in place, etc. I am trying to find if it will work without damaging the unit. That battery model number no longer matches up, so can't tell from the website.
The old extended battery is a 10.8 v 7200mAh. The new one is a 6 cell, 61 Wh of 10.8 v.