There is a subtle difference to the appearance of the threads on the necks as shown below:u003cbr/u003eu003cimg alt=u0022Comparison showing necks with single vs. dual threadsu0022 src=u0022https://www.tregaskiss.com/wp-content/uploads/2020/07/btb_faqs_neck_threads_single_vs_dual.jpgu0022/u003eu003cbr/u003eu003cemu003eu003cspan class=u0022has-inline-color has-cyan-bluish-gray-coloru0022u003eFigure 1u003c/spanu003eu003c/emu003e