>>>HSN code for your product is 8505 and GST for this 18% then your PTC code is A_GEN_STANDARD. it is also suggested go through this link:-
https://www.amzblast.com/chapter/chapter-2-how-to-find-ptc-code/
http://www.exportgenius.in/india-import-duty/neodymium-magnet
https://cleartax.in/s/gst-hsn-lookup