These are well made. Granted, you can go to the dollar store, and if you buy enough calculators and timers, you'll identify a brand that you can reverse engineer out many of these parts for pennies. But for convenience and quality, this is outstanding. No defects after using hundreds.555's, op-amps and regulators are the heart of most electronics today. If your electronics or circuit analysis texts cover op-amps before transistors, get a new book!Regardless of how experienced you are with 555's and op-amps, we can all use a little help and fun, so here are two very tiny, inexpensive "manuals" that will do your heart good while playing with these two amazing components:1. 555 Timer Applications Sourcebook Experiments (Howard Berlin) and2. Timer, Op Amp, and Optoelectronic Circuits & Projects (Forrest Mims III)These are only 120 pages or so and $10 bucks or so, but they will greatly enhance your enjoyment of these components. I probably don't need to mention Forrest Mims, as he's a legend!Happy engineering!