Yes that's it. Old audi A3s rear brake calipers have 10x1 which might be the same as for A2s. I'll get one and compare. Thank you.Floating caliper brake; brake caliper housing; bra... Audi A2 (A2) 2003 year Audi 615025
floating caliper brake<br/>brake caliper housing<br/>brake disc (vented) Audi A2 (A2) 2003 year Audi 615025 spare partsaudi.7zap.com
on this close up schematic for the caliper itself there is a 10x1 part referred to as a "breather valve"
don't know if it is appropriate though.