Which has a bigger cup — Bach 12E or Kelly SKY-SS?

The Kelly SKY-SS has a cup diameter of 24.64 mm / 0.9701 in compared to 24.50 mm / 0.9646 in on the Bach 12E — a difference of 0.14 mm / 0.0055 in. A wider cup generally produces a fuller, darker tone but requires more air support.

How does cup depth compare between Bach 12E and Kelly SKY-SS?

Both mouthpieces share a shallow cup depth, so the sound character from depth alone will be very similar.

Bach 12E vs Kelly SKY-SS

Name: Kelly SKY-SS
Brand: Kelly

The Kelly SKY-SS has a wider cup diameter.

Overall Comparison Cup Diameter Cup Depth Rim Width Throat Diameter Backbore Finish Material

Base metal or construction (e.g. brass, stainless steel, plastic). Influences weight, response, and tone color.

Mouthpiece A

Bach 12E

• Trombone

Material—

Best suited for

📣High-volume projection — open throat for power

Mouthpiece B

Kelly SKY-SS

• Trombone

Lead

Material316 Surgical Stainless Steel

Best suited for

📋Professional lead trombone

Material

The Bach 12E is described as unspecified, and the Kelly SKY-SS as 316 Surgical Stainless Steel. Material affects mass, warmth, and how quickly the piece responds.

Which is better?

Neither mouthpiece clearly dominates the other — the right choice depends on your embouchure, playing style, and the sound you're after. Try both if possible.

Open in interactive tool + Add third mouthpiece Bach 12E details Kelly SKY-SS details Bach 12E equivalents Kelly SKY-SS equivalents

Bach 12E vs Kelly SKY-SS

Material

Playing Characteristics

What Do These Model Names Mean?

What Changes If You Switch?

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