Dougie, they're not; just depends on what brand you buy.
You might want to consider posting these kind of questions in the "General Questions" forum. The BBQ Pit is generally for people who are off on a rant about something or need to give somebody what 'fer. You'll see what I mean if you read some of the other posts.
Congratulations, you are no longer a Junior Member!
...it has never been my way to bother much about things which you can't cure.
- A Connecticut Yankee in King Arthur's Court-Mark Twain