using flatmap to separate array with comma

I have the following array:

[
["Polymeric", "Vehicle Graphics (Basic)"],
["Cast", "Vehicle Graphics (Part Wrap), Vehicle Graphics (Full Wrap)"],
["Polymeric", "Vehicle Graphics (Part Wrap)"]
]

I need this:

[
["Polymeric", "Vehicle Graphics (Basic)"],
["Cast", "Vehicle Graphics (Part Wrap)"],
["Cast", "Vehicle Graphics (Full Wrap)"],
["Polymeric", "Vehicle Graphics (Part Wrap)"]
]

Here’s my code:

const source = [ 
  ["Polymeric", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, "Vehicle Graphics (Basic)"],
  ["Cast", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, "Vehicle Graphics (Part Wrap), Vehicle Graphics (Full Wrap)"],
  ["Polymeric", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, "Vehicle Graphics (Part Wrap)"]
];


source.flatMap(([key, value1, value2, value3, value4, value5, value6, value7, value8, value9, value10, value11, value12, value13, value14, value15, value16]) => { 

  const values = value16.split(', ') 

  var hjk = values.map(singleValue => [key, singleValue])
  console.log(hjk);
})

Here’s a jsfiddle of it working.

Is there a better way to do this? Putting value1, value2 etc seems silly.