Ok for Spigen case this is how it is.
Thin Fit series is the thinnest case out there that provide minimal protection*, usually with exposed sides or buttons. This is good for people whom do not want bulky case, and it is made of hard plastic with matte rubbery surface.
Liquid Crystal case is 2nd in line for thinnest case but not hard plastic, it is made of soft TPU rubber. Which is flexible and bendable. It covers all the area of the phone, but it is of bare minimum or close to 0 protection when it drops. Cause it is so soft, usually the impact from a drop usually will still leave a dent on the phone.
Rugged armor is the 3rd in line for thickness. Unlike like Liquid Crystal, it is matte black and made of much thicker TPU rubber. And has their air cushion at the 4 corners of the case. This offers, good protection all round, yet not that thick and bulky.
Ultra Hybrid is a different approach than the above classic 3 case. Ultra Hybrid balance the need of aesthetics yet maintain good protection without sacrificing by adding more bulk. Ultra hybrid has a transparent hard plastic back and the sides are all thick TPU rubber. It has air cushion at all corners to absorb the impact.
Neo Hybrid is the same as Ultra Hybrid, but instead of TPU rubber for the sides, it uses metal instead. This is to give the "more premium" feel of the metal sides. Also it is made of 2 different pieces, metal rims, and full TPU rubber back cover and sides. But many including my friends have complained about it, as it felt slippery from hand, and not really good to use.
Neo Hybrid Crystal no difference from Neo Hybrid, but instead of plastic and metal in 2 different piece like Neo Hybrid has to offer, Neo Hybrid Crystal offers plastic back, and TPU rubber sides.
Next in line is the complete armor series with no compromise in protection. But however it is very bulky imho. Starting from the slimmest armor series.
Sim Armor is the thinnest 2 piece protection, the body 1st layer is covered with TPU rubber, while the add on piece is a hard plastic cover for the back.
The second thickest will be Slim armor CS, this is thicker because instead of a kickstand like how the Slim Armor has, the Slim armor CS is for Card slots.
And last of all the mother of all armor case, the Tough Armor. This case is not much thicker than the Slim Armor, its only the side rims are thicker than the rest. But this comes in a whole single piece rather than 2 pieces. But some claimed that it is so tough that some said, they drop their phone countless of time, and this case never failed them.
*Typo
