{% for property in collection.current_numeric_properties %}
  {% if property.is_numeric? and property.gt_value %}
    <input type="hidden" name="properties_gt[{{ property.id }}]" value="{{ property.gt_value }}">
  {% endif %}
  {% if property.is_numeric? and property.lt_value %}
    <input type="hidden" name="properties_lt[{{ property.id }}]" value="{{ property.lt_value }}">
  {% endif %}
{% endfor %}