This is a very classic dentoalveolar expander, a quad-helix.

@sergio-oms

which one do you think is better,quad helix or haas appliance?

Ive actually had this expander when i was 9 years old. I wore it for 2 years and it corrected my crossbite. too bad i wasnt told about proper tongue posture when i stopped wearing it. I remember that it made speaking a bit difficult and i had loads of eating restrictions. It also felt pretty uncomfortable. Those rings also leave a mark in your palate for good.

@ruoho

do you think that someone can do mewing with that on his mouth? kind of a difficult answer since you were 9 years old but yes, right? 

@notfunnydidntlaugh

Id say it did a pretty good job. I got lots of forward growth with it but i dont know how much it had expanded my imw. Im going to ask my dentist if i could have the teeth molds back to measure it myself. Im not sure if mewing with that thing in your mouth would feel that comfortable. Id be afraid about hurting my tongue because of of those thin wires. It also looks pretty fragile and id guess it could also irritate the tongue too. Im not sure if its possible to mew with an mse in your mouth but if its possible, then i guess maybe you could mew with the quad helix too.

@ruoho 

I hope it is worth buying...Im 17,5 years old so I guess it can do something in my age.In my country we have only that,hyrax,haas,homeoblock and twinblock….

It wouldn't feel that comfortable but still it would be possible, I guess...

@ruoho

You needed braces to correct the bite,right ? 

i think you need more force at an older age

@mr-mewing

So which palate expander should i get  something like hyrax or haas or schwartz? 

@notfunnydidntlaugh

yes. But like mr.mewing said, i dont think quad helix has enough force. In my country, they would use the RME appliance for people your age.

Posted by: @notfunnydidntlaugh

@sergio-oms

which one do you think is better,quad helix or haas appliance?

It would depend on the age of the patient, the problem and the purpose.

@sergio-oms

Is haas expander for rapid palatal expansion?

Posted by: @notfunnydidntlaugh

@sergio-oms

Is haas expander for rapid palatal expansion?

You know it is... but it that doesn’t mean it necessarily works

@notfunnydidntlaugh hyrax would work i think