Search engines and customers both understand a store better when collections are separated by real product use. Wireless tattoo pens, wired tattoo pens, tattoo pen kits, tattoo needles, tattoo ink, transfer products, accessories, consumables, and machine parts each answer a different buying intent.
Keeping these categories separate reduces keyword overlap, prevents irrelevant products from appearing together, and gives each page a stronger chance to rank for a precise long-tail search.