Thanks for that - Yes - I have that part number also, but the description of "Collet Chuck" is wrong. It's a Reducing Sleve not a collet. As per your photo.
Not sure why they have different part numbers for appparently the same thing. Maybe one is 12mm to 1/4" rather than 1/2" to 1/4". All a bit of a muddle really.
The price also gives it away. The 1/2" and 12mm collets are about $29 in the US - about £29 in the UK - twice as much !!! I imagine a 1/4" collet if it exists would be a similar price.
The reduction sleeves are about $7 / £7.