I would interpret the question as 1" as well, but square drive impact bits aren't going to be found on the Festool Site. There should be some available from the usual suspects like Milwaukee, DeWalt, Apex, Makita, etc. If the question is for shortish Centrotec square drive then it will need to be the Apex ones sold by various dealers. A search for Centrotec square drive here will produce a list of folks who can help with that.