One of the biggest misconceptions is that the standard weight of official casino poker chips is 11.5 grams. It is not. Although there is no single standard weight, all official casino chips are between 8.5 and 10 grams. Authentic clay chips are usually between 9.5-10 grams and ceramic chips are close to 10 grams.
When looking to buy chips, the 11.5 gram poker chips ("Suited/Dice") are usually first ones that people look at. Most 11.5 gram chips are made from ABS composite plastic, which is a compressed plastic material that is highly durable.
These are usually second-class chips at best. Any chips that weigh less than 9 grams deviate too far from official casino weights, and will usually be made out of cheap plastic.
Another misconception with poker chip weight is that heavier chips are higher quality. This is not really true. While the super light chips (2-3 ounces) are really cheap, there is no difference in quality within the 8-14 ounce weight range. It is simply a matter of preference. The chips that are in the lower end of this range (9-10 ounces) are actually considered by most people to be the higher quality chips.