The sizes displayed are jacket sizes. Pant sizes for 36-46 chest will be 6 inches smaller then the jacket size. Pants sizes for 48-52 will be 5 inches smaller, and 54-56 the pant sizes will be 4 inches smaller than the jacket size. Ex. Size 40 Regular Jacket comes with size 34 Waist Pants
If you ever wanted to know what makes a slim fit suit the way it is. There are a number of specifications required. Besides having that early 1960s look going on and tighter fit look, you'll find several details on these slim fit suits to make them look the way that they look.
Let's start with the jacket first. On any suit, not just the slim fitting kind there are style features that make them look the way they look. On a slim fit style we can start with the torso of the jacket. The torso will be an inch to an inch and a half shorter than a standard fit suit jacket which brings the look to a different level. The body will be very tailored to the body for a tighter style fit compared to a regular fit suit.
The next thing you'll find is that on slim fit suit jacket the sleeves are tighter fitting as well and the arm holes are right up to the arm pit for a highly tailored fit. The sleeves will look narrower as well almost like the sleeves are supposed to fit like a glove. If you lift weights and have big muscles this type of suit is just not going to work for you. You're going to need to wear a different type of suit.
Another feature that you can find on slim fit suits are the lapels. As a style statement, you'll find that they usually and almost always have narrow lapels which goes hand in hand with the tight slim fit look which you'll have to wear narrow neck ties to also coincide with the look. That is also and early 1960s throwback look. It all get recycled at some point. The jacket can also feature either double side vents in the back or a single center vent for ease of movement because let's face it. On a slim fit style suit, there isn't much extra material for moving around in.
On the pants, you are not going to see any kind of pleats whatsoever with slim fit suits. None. You're only going to see flat fronts and the waist line will also be a lower rise than a conventional fitting style suit. Usually about an inch lower on the waist than usual with tighter fitting seat and legs that taper off towards the bottom giving the whole slim fit look a finished silhouette.