it defends on the client. if you are using Ragexe. it still use the old idnum2itemdesctable, idnum2itemdisplaynametable and idnum2itemresnametable. but 2012-07-16 and after. it will now use iteminfo but if you are using RagexeRE. the iteminfo start to use from 2012-04-10.
check your itemslotcounttable.txt make it sure that your item has 4 slot there.