None periodic billing plans

I have 3 plans and each one of them has it's own number of points and a price. these plans won't be periodic (not monthly nor yearly ..) My question is how to define a plan with no time interval , in spark's docs I found this : Spark::plan('Pro', 'monthly-pro') ->price(20) ->features([ 'Feature 1', 'Feature 2', 'Feature 3', ]);

but it also says that spark supports monthly and yearly plans, does the code above mean that that's a monthly plan by default? if so, how can I define a plan with no frequency ?