In our shop, we offer three different hardness (soft-0A, medium-5A and firm-10A). Before having it in the hand, the best way to understand how much hard is something is by comparing with known objects. The hardness of our silicone is around the hardness of our bodies, that's why they feel so realistic. So, let’s compare the hardness of our silicone with the hardness of our bodies.
In the following graph, we have a scale (0-90 A) showing how much hard are different body parts (on the softest region, on the left) and several other objects (on the right). Have a look:
Fatty body parts, such as gluteus and belly, are very soft: they deform easily and can be squished. Muscles, when they are relaxed, are also easily squished but, they offer more resistance than fat. Pushing the bones which are cover by a layer fat, like the hip or ribs, give the feeling of slightly more resistance than relaxed muscles. And tensed muscles are slightly harder than these bones. Finally, exposed bones, such the clavicle are the most harder parts of our bodies. Of course, the hardness feeling depends on your own fat quantity and muscle development.
Now, with respect to the silicone, we have seven different hardness, from softer to harder: extra soft, softer, soft, medium, firm, firmer, extra firm. Extra soft and softer feel like a fatty belly, the difference between them is that we use extra soft for masturbators and softer for dildos. Soft feels like relaxed muscle, with some resistance but not much. Medium feels soft but is harder to bend. The firm, like a tensed muscle feels quite hard and, being difficult to bend, doesn’t bend much. Firmer and extra firm, are very rigid and feels hard; the later is only used in special toys with very thin silicone walls.
Mind that, the thicker is the toy, the harder is the feeling: the bigger toys will always feel harder. That is partially the reason because we don't make all sizes in all possible hardness, the big ones become just too much rigid (both to be used and to take them out of the moulds!).