function llms_get_certificate_sizes() {

	$sizes = array(
		// ISO 216 sizes.
		'A3'           => array(
			'name'   => _x( 'A3', 'Paper size name', 'lifterlms' ),
			'width'  => 297,
			'height' => 420,
			'unit'   => 'mm',
		),
		'A4'           => array(
			'name'   => _x( 'A4', 'Paper size name', 'lifterlms' ),
			'width'  => 210,
			'height' => 297,
			'unit'   => 'mm',
		),
		'A5'           => array(
			'name'   => _x( 'A5', 'Paper size name', 'lifterlms' ),
			'width'  => 148,
			'height' => 210,
			'unit'   => 'mm',
		),
		// North American sizes.
		'LETTER'       => array(
			'name'   => _x( 'Letter', 'Paper size name', 'lifterlms' ),
			'width'  => 8.5,
			'height' => 11,
			'unit'   => 'in',
		),
		'LEGAL'        => array(
			'name'   => _x( 'Legal', 'Paper size name', 'lifterlms' ),
			'width'  => 8.5,
			'height' => 14,
			'unit'   => 'in',
		),
		'LEDGER'       => array(
			'name'   => _x( 'Ledger', 'Paper size name', 'lifterlms' ),
			'width'  => 11,
			'height' => 17,
			'unit'   => 'in',
		),
		'USER_DEFINED' => array(
			'name'   => __( 'User defined', 'lifterlms' ),
			'width'  => get_option( 'lifterlms_certificate_default_user_defined_width', 400 ),
			'height' => get_option( 'lifterlms_certificate_default_user_defined_height', 400 ),
			'unit'   => get_option( 'lifterlms_certificate_default_user_defined_unit', 'mm' ),
		),
	);

	/**
	 * Filters registered certificate size options.
	 *
	 * @since 6.0.0
	 *
	 * @param array $sizes Array of registered sizes.
	 */
	return apply_filters( 'llms_certificate_sizes', $sizes );

}