Lower stem diameter

[Nicolai]

Hi,
I'm trying to build my own stem. I got an alu broomstick, that I figure would be perfect for the top part.
Now, for the lower stem, I just want to buy a cheap lower stem from some random detector, so I get it in fibre-composite and with the mount.

My problem is, it's rather difficult for me to find some diameter measurements on these rods. It's not really something listed in the specifications in any manual I've checked.

Are these standard measurements or will I have to rely on luck?

Same goes for upper stems, to find an arm-rest that fits my broomstick.

I've seen a lot of you have built your own stems, do you have any tips on solving the lower stem compatability issue?

[Tim]

I think those fibre lowers are 15mm-5/8" OD on the generic/cheapies, The mids are 17mm-11/16, uppers 19mm-13/16. But the better brands are 17mm lower/19mm mid/21-22mm(15/16") upper.
All these odd sizes make match-ups a bugger, and the hardware stores here only stock 25&19 OD alloy-an engineering shop can order other sizes.
Broomsticks are 22mm OD, extendable lowers, 19mm. Some flimsy broomsticks are 19mm, some heavy duty mop handles 25mm.
You can us an extendable broomstick if you use a foot or so of 19mm non-metallic at the bottom,by whittling it to fit, but they are flimsy.
I use 25mm alloy and 22mm laminated bamboo broomstick lower. You could use this combo as a crowbar, as the bamboo is much stronger than hardwood.
Most search head "ears" are 19-25mm. Those thin lowers have a larger pivot point to suit, but by using 22mm bamboo composite, you can drill and shave it without sacrificing strength.
I make my armrests and brackets from(100mm/4") PVC sewer pipe, molded with a heat-gun. A piece of rubber bike tube glued inside the lower half of the extension bracket to compensate for the size difference. I see no advantage in an expensive screw-lock.
700mmx25mm alloy,900mmx22mm bamboo broomstick. Fold-down handle is also cut off broomstick, with a bike handgrip. Wingnuts and gutter bolts from the hardware store. PVC from the dump. Alloy $10/m, broomstick $5(AUD) This one is no heavier than my Tracker IV.
If you source 25&22mm alloy, & 19mm non-metallic you could make a 3-piece and get overall compressed length down form 950mm total to about 600mm.