Recommended thread number is indicated with the patterns. The numbers are valid for cotton thread brand "Idrija”; for other materials (linen, metalized thread, silk ...) and other brands, contact sellers:
http://www.cipkemojca.com (site is currently only in Slovenian, you can write them in English to info@cipkemojca.com)
The number is informative, there are possible entry errors and differences in materials. Also other thread numbers may be suitable for some patterns.