I have two of these on the go. I found that the citric acid eventually ate through the insert, so I now buy disposable foil inserts (which eventually get pinholes from the acid also). It has not changed the way my yarns dye.
I finished another pair of socks - these were a failed attempt at a self striping sock blank in Vancouver Canucks colours.
In case you are wondering where I got the cute sock blockers, they are available on Etsy, look up BurningImpressions2. Megan Tilitzky lives in 150 Mile House, British Columbia.
Completed another long lost colourway in Maryanne's Socks - this one goes great with denim.
And this is what I have been doing with my leftover yarn after socks are made.