The 140 is big enough to house a Whatsminer 140mm 6000 RPM fan should you want to put one of those beasts on it, but any 140mm fan will work and give you decent airflow.
The 120 fits a standard 120mm case fan which can also come in a large variety of speeds and decibel levels.
The 120 centered does not have mounting holes for screws so you'll need to tape or sort out another method to secure it.
The Three 40 uses three 40mm fans.
The Two 40 uses a two 40mm fans
The Server 40 requires a single high speed server fan.
Sizes- Within 2mm
140 is 142x142x70mm (82.5)
120 is 122x122x70mm (82.5)
120 Centered 128x128x62 (75)
Three 40 is 122x58x28mm (41)
Two 40 is 102x41x28mm (40)
Server 40 is 102x44x30mm (42.5)
() indicate full height including Lip.
Message me for large orders, most shrouds will be printed to order.