Rumaweep 9.5 feet. Brand new in box POS.
I made the mistake of buying in 2018. Installed in 2019, no warranty.
It make a lot of grok grok noise at slow speed 1-2 even if i stripped the "dinner plate" naked.

P.S. I installed many fans in my lifetime, this was my 2nd Bayu 4.

I have a 2014 variant which works beautifully.
POS = Piece of Shite.

Sensa 4 (around RM515), DC brushless. 
https://shopee.com.my/KDK-K14ZW-56-Sensa-4-...5032.5642458864

All AC motor are brushless.
DC motor can be brushed or brushless type so need to make sure its brushless for long life.

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Sensa 4 (DC) is using same blades as Vtouch Jr (AC) and the previous EOL model Sensa 4 (AC).
This 56" blade design makes about 225m3/min wind which is very plentiful.
ABS blade is very quiet. No funny sounds like the POS Bayu 4 scraping against the center core.
Also, the safety device for Vtouch Jr/Sensa is using metal hook to the center core chassis. 

The POS Bayu 4 design is using a "clothes peg wire" as the safety device to prevent blade from flying off. 

You can go up to the Sensa 5 (DC) current model as well. The more fancy Nikko, Kaze are more nice-to-haves and doesn't make more wind lol.
No noticeable difference, I have a whole mix of fans 3-4-5 blades as long as it is not a faulty unit.
Wind sound is silent.

There is some slight differences in power consumption and cfm between the 4- and 5- bladed variants but it is within a few % you won't notice in a blind test.
4-bladed balancing is easier to do. 5-bladed ones more tricky to balance.