I use this extension bar for my CEM25P mount and it helped me achieve balance with a large Bresser Messier AR-127L telescope (8kg).

There's not all that much to say about a counterweight bar extension. It's the right diameter, the advertised length and it has the right threads top and bottom. It looks like it's made from stainless steel.

Moreover, my mount is an iEQ30 Pro, not a CEM25 or a ZEQ25, but if you look hard at iOptron's on-line info you find that the extension is supposed to fit, which it does. In fact, it seems to be exactly the same extension bar that they sold for the iEQ30 Pro when that was their flagship "30" mount (3 weeks ago?).

In practice it fits as expected, with only a very slight misalignment of the bar axes at the join. You can just feel it, and a weight that just slides freely up and down the original bar needs an extra 1/4, or thereabouts, turn of the locking screw to get it over the bump.