original G5. What type of response system? (edit...found answer)

Noticed my G5 had no pad on one side, while the other side has something that does not look like a pad. Looks more like the flow-able stuff I have read about here. If I purchase YYF standard pads will they work in an original G5?

edit…guess I should have “searched” first! Read that the 19mm YYF pads will work.