Spectra is super strong braid used for securing the trailing hook on a stinger or strung-out style fly.
Coated Spectra is stiff and will keep the stinger hook suspended directly behind the fly. It is used for flies like Stinger Clousers where you don't want the hook flopping around. The 20 Lb is for #6 hooks and smaller. The 30 lb is for #4 hooks and larger. 15 feet per pack.
Spectra (uncoated) is a flexible material and is used on flies where movement is desired. MOAL Leeches, Dolly Llamas & String Leeches all use 40 Lb Spectra. 20 feet per package