GST Registration

You need GST registration. Turnover limit is ₹20 lakhs.

Interstate supply of goods therefore gst is compulsory

Interstate supply upto 10 lakh is exempt for COMPULSORY GST registration. Normal GST REGISTRATION LIMIT IS 40 lakh for goods and 20 lakh for services.

If You will make supply to inter state then GST registration is must without threshold limit...

In case of interstate supply of goods Gst registration is compulsory without any threshold limit.

As per notification no. 10/2017 if a person makes inter state supply of service upto 20 lakh and total turnover of that person doesn't exceeds 20 lakh ( 10 lakh for special category states) on all India basis then he/she is not required to get compulsorily registered.
There is no threshold limit specified for Supplier Of Goods.

Benefit of 40 Lakh limit (Notification No 10/2019.)is not available to those who require to get compulsorily registered U/s 24 of C.G.S.T Act. Since you are making Interstate Sale,you are covered under section 24.

In case of interstate supply.... registration is mandatory irrespective of turnover