As others have mentioned, it is indeed finer than the classic red ILLY, resulting in the need for greater pressure to extract the coffee. This may be an issue for weaker espresso machines, but for stronger ones, it is better because the flow is faster and the coffee is more watery with less bitterness. I have a vintage La Cimbali at home and this coffee suits it perfectly. I should note that in the past (5+ years ago), the classic red had a similar grind. Also, in the last 2 years, the red ILLYs (in the 250g metal tin) have had many quality inconsistencies. Some come without nitrogen, while many come with a little, resulting in them either being already stale or losing their aroma faster than before.

However, the Decaf ones have a very consistent quality (so far) and although I was very negative about the idea of decaffeinated coffee, after several trials in an attempt to solve the problem that arose with the Red Classic, I found that it surpasses the red both in aroma (when still in the tin) and in the aroma and taste of the extract (provided that the boiler pressure is sufficient). In comparison (Red vs Blue), they also have a slight difference in color inside the tin, which may be due to different roasting.

As for the caffeine, I have not seen any difference at all (with or without), which surprised me greatly after 30+ years of consuming 6 ristretto shots of RED Classic Illy daily. I really did not expect that