What type of PVC is best for a rail?

[chubwagon]

So yesterday I went by my local hardware store and browsed their extensive selection of PVC. I figured I wanted a thicker tube (around 4" diameter), so I looked at my options. Expecting to find just one type of PVC tube, I was shocked at the many different types. So my question to you guys is what is the best type of PVC for rails and by this I mean thickness, color, hardness, anything.

 

[cultrara]

The thicker and harder the better. Just buy the standard looking white stuff.

 

[fredyferl]

the big blue ones are the best, but you can't really buy them, you need to find them

 

[WillyTheKid]

Buy the gray conduit stuff. It's a little softer so it doesn't crack as easily and still slides well. Any kind would work though

 

[will_powder]

I always go ABS black and it's always been good to me both in the summer and in the winter

 

[cheerio]

black and hard...

 

[ThatBrokeSkiKid]

10ft length 8in diameter blue plumbing pvc. I'm still trying to get my hands on some