We recently took into stock some convenient 2 oz bottles of Stan's NoTube Tire Sealant. The description of this sealant as posted on Stan's website is pretty concise, and there's really not much to add except to say that we're selling it for $5 a pop, so we're pasting the official description here:
Just two ounces of Stan's Tire Sealant in a converted standard tire or a tubeless tire can repair up to a 1/4" hole instantly.
Pre-measured and ready to apply to one bicycle tire.
Stan’s Tire Sealant will stay liquid in a mountain bike tire with a thin casing for two to seven months on average. Riding in arid climates or storing the bike in a hot area will require more frequent monitoring of sealant levels. Special anti-freeze agents allow the sealant to be used in environments as cold as -30° F.