On my 650 I took off the OEM grip, then used a hacksaw blade to cut off the flange in a couple places, then used a file to file the remaining ridge down to the size of the tube. Not as hard as it sounds - plastic cuts easy.

On the 250 used the Zeta tube for the quick turn.

 

I thought aluminum was the sheet as well and I learned it sucked.
My story; 20 years or so ago I put and aluminum throttle tube on my 89 RM250 because it was an upgrade and cool. So I was out riding like I always was and the front washed out handle bar went in to a tree/ground. Not a real bad crash maybe 25 mph or so. When the handle bar hit the ground or the tree (do not know which first) it bent the throttle tube into the handle bar at an almost pinned state. The bike then spun around on the ground like a possessed top tell it got tangled up in Manzanita bushes that tangled around everything which killed the motor. I will never forget watching my bike spin into everything and there was not a thing I could do and where I grew up it was mostly red cinder or volcanic dirt so my bike looked like someone drug it down the blacktop behind there tuck.

Had to share and also Pro Motion tubes I think are made from nylon they do not shatter like the plastic ones.

 

For what it's worth, I can confirm that the motion pro 01-0094 worked on my 2009 KLX250S.

 

I can confirm the Zeta quick turn is quicker action... I like that. I hate having to grab a second grip for full throttle. Probably stick one on the KLX650 this summer.