Bulb size question

[poly rugby]

Quick question. I have a 70w MH HQI system set up for my nano. If I want to upgrade to a 150w MH HQI, would I simply need to change the ballast and bulb? Is the 70w HQI bulb the same size as the 150w HQI? Will the 150w fit in the 70w Mounting bracket.

Thanks in advance