The 68845NV basic set includes enough components to build any two of the basic acid anhydrides which have the general formula: RC(O)OC(O)R.
Every Orbit molecular model set sold by Indigo Instruments is fully compatible with others you might own. You can replenish any set or customize it with Genuine Cochranes of Oxford Orbit Atoms.
I've had consistently great service from this company. Our students seem to really appreciate the reasonable price. In the years that we've used this product, not one has been returned due to defects.
Considering how many of these we sell to schools every year, that is high praise indeed. Thanks letting us know.