Older kits were never moulded with metal detail, and photo-etched parts at 1:400 put that right. The shelf is built around universal railings in several national patterns, ships' ladders and stairs, and an upgrade set for a celebrated ocean liner. Universal frets can be used again and again on any hull in this scale, so one purchase will serve a whole shelf of ships rather than a single build.
1:400 rests on kits with long production histories, and on those a metal railing makes the biggest single jump: the silhouette finally gains the lines along the decks that every real ship has. Kits to upgrade are in 1:400 and 1:450 ship model kits, and the complete brass catalogue is under ship photo-etched parts. The second favour you can do a veteran kit is a 1:400 wooden deck.