De or het surfkleding?

The correct Dutch article is:

de surfkleding

Rule Words ending in -ing: almost always de. See the rule

How to use surfkleding

the surfkledingde surfkleding
this surfkledingdeze surfkleding
that surfkledingdie surfkleding
our surfkledingonze surfkleding
your surfkledingjouw surfkleding
every surfkledingelke surfkleding
which surfkleding?welke surfkleding?
a big surfkleding / the big surfkledingeen grote surfkleding, de grote surfkleding