Modifiers matching knob:

• spherical,
• round,
• plastic,

Simple categories matching plastic:

• layer,
• clay,
• material,
• matter,
• part,
• item,
• product,
• container,
• cap,
• crate,
• pot,
• ornament,
• formation,
• sheath,
• cone,
• mold,
• article,
• cell,
• iud,
• coating,
• spar,
• procedure,
• rod,
• object,
• machine,
• system,
• toy,
• trait,
• tableware,
• jewelry,
• dishware,
• surface,
• change,
• fixture,
• knob,
• wheelchair,
• cloth,
• figure,
• particle,
• process,
• jug,
• weapon,
• hardware,
• framework,
• block,
• statue,
• garment,
• monomer,
• surgery,
• filament,
• tape,
• disease,
• manufacture,
• chair,
• drum,
• belt,
• band,
• ware,
• appliance,
• property,
• implement,
• chains,
• machinery,
• mug,
• elements,
• web,
• area,
• tag,
• waste,
• substance,
• card,
• accessory,
• characteristic,
• bottle,
• dish,
• paper,
• foam,
• composition,
• thing,
• syndrome,
• casing,
• stuff,
• merchandise,
• carrier,
• detail,
• adhesive,
• panel,
• deformation,
• tubing,
• cooler,
• bit,
• packing,
• body,
• plaything,
• shape,
• tarpaulin,
• footwear,
• mesh,
• sprayer,
• trinket,
• fat,
• strip,
• wrapping,
• case,
• tube,
• frame,
• hinge,
• lense,
• covering,
• substrate,
• restoration,
• sleeve,
• display,
• nut,
• denture,
• core,
• clock,
• tub,
• scraper,
• enclosure,
• pipe,
• carton,
• fastener,
• chemical,
• diaphragm,
• disc,
• form,
• tray,
• sack,
• sheeting,
• toiletry,
• packaging,
• activity,
• mirror,
• decoration,
• tool,
• fiber,
• structure,
• constituent,
• strap,
• mounting,
• molding,
• hanger,
• gear,
• animal,
• equipment,
• tank,
• doll,
• polyurethane,
• organizer,
• supply,
• jar,
• condition,
• bait,
• soil,
• creature,
• medium,
• solid,
• cabinet,
• project,
• fitting,
• bin,
• instrument,
• plate,
• clothing,
• resin,
• member,
• food,
• behavior,
• piece,
• commodity,
• portion,
• cutlery,
• wedge,
• beads,
• utensil,
• signal,
• section,
• flooring,
• component,
• assembly,
• event,
• fabric,
• lure,
• bed,
• package,
• polymer,
• sheet,
• washer,
• compound,
• bowl,
• works,
• manoeuvre,
• metal,
• profile,
• box,
• furniture,
• mass,