So these aren't the best cables you can buy.  For that you'll have to go to an electrical or welding supply company and you will PAY!  Probably between 3 and 5 times what these cost!  So unless you plan to start a towing service and need cables that will see daily use, I'd say these are gonna work for you.(Update: After compairing them to the 4ga cables I bought a month or so back for my car, they don't really seem that much thicker...  That's said they are MUCH heavier!  The individual stranding is of a thicker gauge than the other model so I'm guessing that's why the thickness isn't much more...)What I like:--Length - I bought these for a half-ton pickup.  Why?  Because it never fails that your battery will fail to start your engine when your parked in a packed lot with cars on all sides.  Rather than pushing a 3 ton vehicle out you pull the booster vehicle in as close as you can and let the length work for you.--Heft - these cables are no joke.  It's a workhorse grade cable that lets plenty of energy flow.  When trying to start a 5.7L V8, that's kinda important.--Solid Clamps - Unlike some of the other reviews, I don't have a problem opening my parrot clamps with one hand.  But their hardly weak, they'll clamp solid and stay put!(Update: If you really need 2ga booster cables and your skeptical of these, Deka makes a set of 2ga cables for around $150.  I have no personal experence with them but I have a little with the Deka name and they seem pretty good.)What I don't like:--Stiffness - They're not as flexible as I was hoping.  But about as flexible as I expected.  True welding cable in 2ga is about $3 per foot and per cable.  That's why the best jumper cables cost $200+.  Still I was hoping for a little thinner stranding to promote flexibilty.--Cable to Clamp - Like other reviews have mentioned the cable doesn't go all the way to a copper contact connected to the jaws.  Instead.  It's screwed to the body of the clamp then the copper jaws are also screwed to the body.  Still fine I'm sure.So why buy these cables aren't they overkill?  I've had this argument with people before: "My 6ga cheapies start my truck fine."  Well I will attempt to addess this.  As the number in terms of gauge decreases the ammount of conductor increases.  In other words 2ga has more (perhaps 50-100% more) conductor than 4ga.  This doesn't automatically equate to twice as much power but it does certainly allow more power to flow safely.  For those that aren't aware (and I'm not an electrical engineer here), resistance is the enemy of all electrical circuts.  Resistance translates to heat in the same way that friction does when two physical surfaces rub together.  Five basic factors contribute to resistance in a give curcuit and determine the appropriate line size.  Ambient temperature, conductor, line distance, voltage, and amperage.  Ambient temp we have no control over.  Hot is bad so just assume the worst.  This means bigger cable to overcome the additon resistance heat is producing.  Conductor of these is copper so that's good.  You want pure or at least a high purity mix of copper in this type of conductor.  Distance and voltage.  One of these cable's strengths also happens to be a weakness.  Total run length for this circut is 50'.  Pretty long for a low voltage system like 12VDC.  The higher the voltage, the longer it can run on a given gauge wire without encountering too much voltage drop.  12VDC drops voltage on a circuit in a realatively short distance.  So heaiver gauge lines are needed to prevent this.  Amperage is also a big consideration.  The more amps a load pulls the more resistance the circut will generate.  Basically on a small wire, a large load will generate a lot of heat and one of two things will happen. 1) the wire will melt and/or catch on fire.  2) The load your trying to power won't work.  And make no mistake, starting even a small engine takes a LOT of energy!  So bringing it all together.  Large load, low voltage (that we don't want to make in lower), and a long distance run means that you wan the heaviest cables you can find.  Addressing the orignal question and statment.  6' 6ga cables might start your small-block fine.  But if you want or need the extra length, you need to consider heavy gauge cables.  That said I've personally seen light duty cables melt and smoke from starting an engine too big for them.Are these right for you?  So these will run you close to $100 shipped...do you actaully need them?  I own both these and the Coleman 4ga 25' booster cables.  Having no offical training and with no real sizing charts on the packaging I would say this.  The 4ga will do you fine at the 25' length for engines up to 5-liters or so (and honestly probably up to about 6L as well.)  Anything bigger than that and you should be considering these or something even better.Also protect your investment.  Buy a cable bag for them to keep them neat and protected.  Also keep the twist ties that came with them to keep them organized inside your bag.  I have the Arsenal #5888 cable organizer and it works great for this.  Remember too to clean and inspect your cables after each use to prolong their life and keep you safe.