Rubber contact strip for synthesizer keys, 4-note strip. This strip contains carbon contacts inside each "bubble". When a key is depressed, the key presses down on the bubble, and the carbon makes contact with the circuit board (the keyboard "contact board"). This type of strip has two contacts per note; one is to play the note itself, the other is to indicate the velocity at which the note was struck. This strip is used but working well. This strip also fits the Roland S-10/S-50/W-30, Korg PA1,2 & 3x series, SP-200, Alesis QS8, Kurzweil K2000 and several other keyboards.