From Loren Wiseman's website:
The 20-ton launch is among the smallest general utility craft in common use, manufactured in many configurations throughout known space. This publication deals with nine common variants (including an armed version -- the 20-ton gig). This book contains nine variants on the same basic design, and includes deckplans (scaled at 1/2" = 1.5 meters) and game ratings for Classic Traveller, MegaTraveller, and GURPS Traveller.
In addition to the standard, unmodified launch, this book describes:
The Lifeboat variant, carried by small merchant starships, and equipped with emergency low berths for 24 passengers.
The Liaison Launch, for use as a mobile office/headquarters by business magnates or military officers.
The Survey Launch, used by scientific missions and bases.
The Search & Rescue variant.
The Hunting Launch, carried by yachts and safari ships.
The Retail Launch, used by retailers in remote areas as a mobile "general store."
The Estate variant, used by managers of large plantations, factory farms, estates, and wilderness preserves.
The Gig (Armed Launch).