Retailer listing reveals first details on Rock Band 2 cymbal add-ons

Anyone who picked up the new Rock Band 2 drum peripheral may be wondering what they're going to do with those ports on the back of the kit. The answer: you're going to attach cymbals to it. But what do they look like? How do they work? Where do babies come from?

An online GameStop listing has the first (yet small) image of the official cymbal add-ons, produced by Mad Catz, along with the first solid information on the set. For $29.99, you'll be able to pick up two velocity sensitive cymbals that can be used as a crash, a ride, or hi-hat. 

The kit comes with "easy-to-install" mounting brackets that should let you position the cymbals as you see fit. Below is a quick run down the features, taken directly from the online listing: 

• Crash, ride and hi-hat cymbals.
• Velocity-sensitive for precise drumming
• Adjustable height
• Easy-to-install clamps for quick setup.
• 2 x Cymbals
• 1 x Double Clamp
• 1 x Single Clamp
• 2 x Colored Wing Nuts
• User Guide

So here's my question -- the new drum kit is expandable for up to three cymbals. If I want to actually have three cymbals on my kit, do I need to buy two packages of two cymbals? And then what exactly are we supposed to do with the extra cymbal?