150watt DE on a 175watt ballast?

[Giovanni]

Any one used a 150watt DE on a 175watt ballast? I picked up a 175 setup today and have two extra 150 bulbs. They look like the same size. Just don't think I could be the first one to want to try this.

Thanks in advance.

[piscivorous]

Some ballasts are made to run both DE 150 or SE 175s.....I don't know which are which or what might make some able to do this and others not???

[Giovanni]

I have a DE 175 ballast. I guess I should have said DE for both. Thanks