The Type XXI submarine came too late (thankfully) to influence the outcome of the Battle of the Atlantic. But its revolutionary design was the basis of post war submarine development up to the development of nuclear power. One revolutionary feature was its method of construction using prefabricated sections built at dispersed locations and only brought together late in the construction process limiting the vulnerability of the submarine to destruction on the slipway.
Only one Type XXI suceeded in becoming operational before the war's end.
Generally a simple model to build. Pieces fit well. The retractable dive planes are fragile and break easily so are best fixed deployed or stowed.