It appears that Caudabe is moving the Synthesis and Sheath closer to each other. Used to be the Synthesis was more robust with the harder material on the back. Now with the felt lining on the Sheath they've become similar in weight with the Synthesis actually being slightly smaller in some of the dimensions.
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Here you can see how much thicker the 15 PM Sheath (R) is than the same model for the iPhone 12. It also weighs considerably more - 46g vs. 26g.
I had a Sheath last year on my 14 Pro Max, and just got the Synthesis for my 15 Pro Max. I know it's not Apples to Apples, but it does seem the Caudabe case get a little thicker each year. This case is 45gr.
I appreciate that a case that provides mid-level drop protection needs to have some thickness, but I was surprised that this years case is this heavy. It does fit well, the buttons work fine, and the grip is nice. It just adds noticable weight to a Pro Max. Even with the 15 series dropping some weight this year, the 15 Pro Max with a Synthesis case, is a little heavy.
Fortunately, I use my phone naked most of the time (the phone, not me...). I did want a case with mid-level protection for those times when I run a higher risk of dropping it (occasional use). So I'm not complainingg about the weight really, but I am surprised that the weight is going up each year. Once Magsafe was implemented, I thought the weight would remain stable.