General Products hull
The most famous (and most profitable) items produced by General Products are General Products hulls, which are advertised as being impervious to anything apart from visible light (as defined by wavelengths visible to any of the species which are customers of General Products), antimatter, and gravity. The hulls are advertised as being capable of passing through the upper atmosphere of a star without damage, although the contents may become overcooked (but see below for a solution to this problem). The company even offers a guarantee that, should anything harm you within a General Products hull as a result of a failure of these specifications, you (or your estate) will receive a very large sum of money ("tens of millions" of "stars" in the event of a death, with a "star" having value roughly equivalent to one United States dollar in the middle of the 20th century). In the history of General Products this indemnity has been claimed only once, by Gregory Pelton, whose hull failed under extremely unusual circumstances (see Flatlander).
- Nothing, but nothing, can get through a General Products hull. No kind of electromagnetic energy except visible light. No kind of matter, from the smallest subatomic particle to the fastest meteor. That's what the company's advertisements claim, and the guarantee backs them up. I've never doubted it, and I've never heard of a General Products hull being damaged by a weapon or by anything else.
As a GP hull is transparent, most humans paint some or all of the hull to provide some privacy and to prevent problems associated with FTL travel through hyperspace and exposure to the "blind spot". To provide further protection, the hulls are normally lined with 'flare shielding', which instantly becomes reflective to any of the transmitted visible light wavelengths should the intensity rise above a certain threshold.
Furthermore, since the Puppeteers are careful to an extreme degree to avoid any risk at all, they don't trust even these hulls completely. They have therefore installed in at least two (and possibly all) of their ships a Slaver Stasis field, which stops time inside the hull instantly should anything bad happen, and keeps it stopped until the bad thing goes away. In the absence of time, nothing can possibly affect the contents of the Stasis field until it turns itself off. Indeed, Louis Wu speculates that a ship with its Stasis field on would be able to handily survive a second big bang (though several stories cast doubt on this).
A General Products hull is "an artificially-generated giant molecule, with the inter-atomic bonds artificially strengthened", causing the hull to resist "any kind of impact, and heat in the hundreds of thousands of degrees" (from Flatlander). In Fleet of Worlds, the characters learn that the bonds of the giant molecule are "artificially strengthened" by a small power plant in the hull. By aiming a very powerful laser at it (since GP hulls are transparent to visible light), one can destroy the power plant, and destroy the hull. Gravity attracts the hull and its contents normally, but not even close approach to the event horizon of a black hole can damage the hull. However, tidal stress will kill anything outside the ship's center of mass (from Neutron Star), and the hull probably could not survive entering a black hole's singularity. Furthermore, a General Products hull can be destroyed by antimatter. Hyperdrive affects General Products hulls, since it is used by the ships to travel. From the text of stories involving stasis boxes, it is implied that the "hyperwave" pulses used for probing for them are not reflected by General Products hulls, though whether these are absorbed or penetrate is unclear.
There are four General Products' hull models available for sale, each of which can easily be adapted and customised to any specific need.
GP #1 hull 
GP #2 hull 
A #2 GP hull is a cylinder 300 feet (91 m) long and 20 feet (6.1 m) wide, pointed at both ends and with a slight "wasp-waist" constriction near the tail. The Lying Bastard, the landing vessel in which Nessus, Louis Wu, Teela Brown and Speaker-to-Animals crash-land on the Ringworld, is based on a modified #2 hull, specifically designed with most of the flight equipment and thrusters on the outside, to minimise the number of breaks in the hull, allowing a Slaver stasis field to be fitted to the inside of the ship, protecting the occupants from any danger (by freezing them in stasis in the event of attack, for example).
GP #3 hull 
A #3 GP is a cylinder with rounded ends and a flattened belly. It is opined in Ringworld that a #3 hull makes a good multi-crewed passenger ship. Before acquiring the Lying Bastard, the Ringworld expeditionaries transfer from the Long Shot to the Puppeteer homeworld in a ship based on a #3 hull. The Hot Needle of Inquiry which carried Chmeee, Louis Wu, and the Hindmost from Known Space to the Ringworld in The Ringworld Engineers also had a #3 hull. The Hot Needle of Inquiry is described as being 110 feet (34 m) across in Ringworld's Children.
GP #4 hull 
A #4 GP hull is a transparent sphere around 1,000 feet (300 m) in diameter; it is the largest ship size ever built in Known Space (though Ringworld 1 refers to some STL "slowboat" colony ships as being larger and Louis Wu's internal monologue indicates the ship is more than a mile in diameter ). Due to the large size and their cost, they are generally used only for colonisation projects. The Long Shot — the ship flown to the galactic core by Beowulf Shaeffer in the short story At the Core and flown to the Pierson's Puppeteers' fleet of worlds by Louis Wu, Speaker to Animals, Teela Brown, and Nessus in Ringworld — is built inside a #4 General Products hull, most of which is filled with the advanced "quantum II" hyperdrive leaving only a small two-chamber living area.
- Slesar, Henry. The Success Machine, Amazing Stories, September 1957
- Materials science in science fiction