Pros: Price, consistency, usability
Cons: Non-sustainable (peat)
General Hydroponics Rapid Rooter Plugs is a great media when it comes to cloning. The substrate is fairly consistent in density, therefore it is consistent in moisture retention. They advertise that the matrix provides an optimal air-to-water ratio, which results in explosive early root growth. I will confirm this to be accurate because 10 out of the 12 cuttings that were placed in the plugs rooted without the aid of a cloning gel.
The only downside to this product is the main ingredient: peat moss. I could not confirm if the manufacturer uses the Canadian Sphagnum Peat Moss Association or another respectable association as their supply. If you know, leave a comment below to further the discussion!
All points considered, this product works and therefore it is a great tool to have on hand for hard to clone plants!