Pass category on createOrder

[cxxxv1]

What is the proper way to pass a 'CATEGORY' for later use in reporting transactions. This is what I have so far:

paypal.Buttons({

fundingSource: paypal.FUNDING.PAYPAL,

createOrder: function(data, actions) {
return actions.order.create({
purchase_units: [{
amount: {
value: ppFEE
},
description: 'TICKET',
}]
});
},

onApprove: function(data, actions) {
return actions.order.capture().then(function(details) {
if (details.status == "COMPLETED"){

FinishRegistration();
}
});
}

}).render('#paypal-button');