This is a great item it allows you to farm easier in two ways. One you can place wards to see incoming ganks this isn't just beneficial for yourself but your whole team, the less you die the happier your team will be and having a ward to see an incoming gank will save you multiple times. Two the chance to deal 500 damage to a minion. Damage, Armor, Lifesteal all great things here.

Hands down probably the better pick of boots, either roll with mercury's treads if the team has alot of crowd control (stuns, slows, fears, etc) or use ninja tabi the extra dodge is great with nimbleness.

Your main defensive item the extra health will serve you greatly. The added damage is also nice and the ability to slow champions by 40-30% movement speed will net you a few kills.

This is your main offensive item, the damage, attack speed and -45 armor at 3 stacks to your target will greatly increase your capability in team fights in shredding the squishies and even farming minions or helping your team grab buffs or soloing dragon mid, late game its all good.

The Black Cleaver + Stark's Fervor is a great combination try it squishies will drop quick not only will this give yourself major benefits in damage but it will also help your team while in team fights for the damage they put out as well.

If your winning the game people will more then likely forfeit before you get a chance to make this item but this is your final item on the list. Once again it has everything Lee Sin needs to dominate the fields, damage, attack speed, and a whopping 4% of the targets maximum health in magic damage + armor.

Great item for tanking for any kind of enemy team composition I highly recommend it for Lee Sin as it is in all of my tank builds.

A decent item only if mostly everybody on the enemy composition is attack damage, say around 4 of the enemy is attack damage and one is a tank I would use these.

Overall great item high magic resistance for taking big AP hits and 40 hp /5 very good item exspecially if the enemy team is mostly ability power I would recommend this.

Extremely important item if the enemy team is 80% attack damage this will rip them apart given the fact that they target you, but if you're doing your job as a tank right they will attack you no doubt.

Great item for tanking as a Lee Sin gives a decent amount of health points, armor, and a nice bonus of 40 damage every second to nearby enemies.

The debuff removal from this item makes it good enough, but with the added magic resistance standing ontop of that makes it a must in most cases unless the enemy team is all attack damage. Mercury's treads + the active is awesome for tanking.

Great item to build if you're going up against a good combination of attack damage characters, I use it in my balanced build due to the fact the hp/5 seconds and the small amount of added hp + the unique active really saves you alot.

I use this in some of my tanking builds because of the health points and hp/5 seconds, although be extremely careful with this item if the enemy team has madred's bloodrazor you may want to reconsider and buy something else that best suits the enemy team composition.

If its mid game and you feel like your damage isn't quite up to par and you feel safe without a ward you can drop your Wriggle's Lantern and pick one of these up the 40% armor pen will help you alot.

Other team all AD and getting focused? Switch your Frozen Mallet out with Thornmail, just remember to pick up a red buff before team fights to counter the loss of the freezing from Frozen Mallet.

Given that the other team doesn't have a Madred's Bloodrazor by mid or late game, if your feeling squishy you may want to pick this up the added health and passive from it stacks up good, once again take this instead of Frozen Mallet.

Getting focused and need more magic & armor defense get this it will help you. Again drop the Frozen Mallet for this.

Other team is all AP or mostly AP grab this instead of Frozen Mallet but remember to try to grab a red buff before team fights its not 100% needed because you have "ee" but it can make the difference.

Stealth champions may need to be killed you'll need this to find them.

• Note when in the loading screen if you are taking a tank Lee Sin you SHOULD be able to view the enemy team composition and say ap/ad/tank, and then be able to tell yourself what kind of tanking build you will need example if you will need more magic defense then defense obviously if 4/5 of the enemy team is attack damage you will want to stack attack damage don't always go 100% off of my premade builds because they will not work 100% with every team composition they are only to give you a base guideline of what kind of items you should be looking into for different types of situations.
  
• When up against an enemy tower and they are turret hugging but one is low have your lane partner stay out of turret range but close enough for your 'w', "qq" in and 'w' back to your lane partner for an easy kill.
  
  
• When your own lane is being pushed against your tower the same method can be used. Tell your lane partner to stand near your tower or in range of your 'w', try to land a "qq" on a champion near the tower if there is to many minions and you feel confident flash -> exhaust -> 'R' (ultimate) them back into your tower -> 'w' back to your lane partner -> "ee" to cripple and if necessary if your lane partner has any exhaust spells have him / her use it at that point.
  
  
• When concerning his passive you should time abilities when using this because if you use an ability and get his passive and then immidiately use another ability before using the current stacks the stacks will just be 2 again which is fine but you get more benefit from using say 'q' -> "pp" -> "qq" -> "pp", compared to 'q' -> "qq" ->"pp". The method before i posted works very well for downing towers.