This is a Bach 1C with a ReST-M2 coating applied on 25/24. The coating slightly narrows the cup, making it approximately equivalent to a 1-1/4C. I'm selling it because it's a bit too large for me. There are small scratches on the part that touches the instrument. Bach Symphonic Throat 25 Backbore 24 Selling at a bargain price to clear out items. Bach 1C 1 1/4C One Quarter Trumpet Mouthpiece Symphonic ReST M2 Resin Coating Metal Allergy Prevention Metal Allergy Allergy Measures