$(document).ready( function() {
  $('.linkerkant .block .inhoud').each( function() {
    var curIndex = $('.linkerkant .block .inhoud').index(this);
    if($('.rechterkant .block .inhoud').size() > curIndex) {
      var myCompanion = $($('.rechterkant .block .inhoud')[curIndex]);
      var myHeight = $(this).height();
      var myCompanionsHeight = $(myCompanion).height();

      if (myHeight > myCompanionsHeight) {
        $(myCompanion).height(myHeight);
      }
      else {
        $(this).height(myCompanionsHeight);
      }
    }
  });
});