Look at the size of their filter you should able to know
Maybe you can ask for sample lab test results, i am sure they can't show you any.

all drinking filters can only reduce heavy metal like 90-99% and not eliminate.
Basic carbon block can easily reduce
1) Chlorine
2) Bad taste and odor
3) Chloramines
4) Fine sediment
5) Giardia and Cryptosporidium cysts
6) Organic chemicals such as pesticides and solvents
7) Heavy metals such as lead and mercury
source : http://www.wqpmag.com/carbon-block-manufacturing

better quality & quantity carbon blocks or higher quality filtration will have higher % of reduction, never seen anything can 100% remove

Good if they can provide the report.
The size is about your hand palm.
Most of the water filter can reduce heavy metals.
Tap water is already mild alkaline as there are minerals present.
Another thing is the carbon material and built up, is it block or loose carbon powder? Ask them to show you. I am not sure for Cuckoo. Carbon block is more effective compared to loose powder.

Is there any others option other than Espring in term of water quality and price??

why only have few water filter using UV???

any negative effect to us

tq