revised/updated 12/8/2011, thursday: seidio's extended battery cover for my captivate was crappy and loose. my review is not for the seidio extended battery life - i am sure the battery will be excellent. i bought the complete set, the extended battery and cover for $70. my concern is for the cover only. if you want a side by side comparison of battery life of the $70 3,200mAh seidio vs. the $99 3,200mAh mungen, sorry, it won't be here. since i am not gizmodo, consumer reports or a testing center. to compare the current extended batteries offered by gtmax, seidio and mungen side by side, if you want to spend a few hundred dollars to buy, test video them, go for it!!! i certainly would be curious. mungen is backordered until 12/16/2011, and @ $99, way too expensive for me. seidio is offering free u.s.p.s. shipping for christmas, but i choose the fed ex super saver for $7.30 because i am OCD with my battery. i ordered @ 9 am pacific monday, seidio shipped out the same day, and delivery was around noon today pacific, thursday. only 3 days point to point is pretty fast turnaround i think. i do not like the fact mungen direct is only in hong kong, and to call, which i tried, their phone number was wrong, and you then can only email them. if there is an issue or defect, i have to wait for help and shipping a replacement door or battery from hong kong??? and pay $99??? if they are in the usa, please let me know..... and no, i do not do amazon for fairly expensive items which may have problems and/or defects, huge time zone differences, bla, bla, bla. see porcupineli's original post (op) for the official company links to both seidio and mungen i posted in my comments. porcupineli's post is titled "1800mAh Mugen Power extended battery is out for AT&T SGS2:" moving on, here are my observations: 1. the extended battery and battery cover came packed separately. you can buy the sgs2 seidio cover only for $14.95, sku# bvy32ssg2a-bk. the sku# for the battery only is bas132ssg2a. funny, it would be interesting to try a cheaper extended battery, as in a post regarding the GTmax extended battery, which is under $20 and use the seidio cover. the gtmax blog link is: http://androidforums.com/samsung-galaxy-s2-t/445848-gtmax-3500mah-battery-working-great.html also, i wonder if people who bought a $99 mungen could use seidio's cover with it? who knows...... or if people who bought the seidio can use a mungen cover... hmmmmmmm. 2. the seidio extended battery cover has the signature seidio velvety feel, but actually fits too tightly, in my opinion. i noticed in the gtmax video gmax had a very shiney, hard looking, non-textured cover, and looked cheap in my opinion. but for around $20, what do you really expect? in a mungen video, mungen's cover looked really nice with a textured finish. sgs2 seidio cover is it does not show normal (non greasy) fingerprints or minute scratches. yes, seidio's cover can be scratched, but not like hard, shiny plastic. the velvety seidio feel allows for an easy to hold grip, and has verticle sides. gtmax has a very bulky looking bulbous cover. mungen has nicely sloped sides for their extended battery cover (per videos of gtmax and mungen). 3. MAKE SURE TO SPEND 10 MINUTES OR MORE TO GENTLY AND VERY CAREFULLY CAREFULLY INSTALL SEIDIO'S BATTERY DOOR!! it honestly took me over 10 minutes since i did not want to break off the male (proturding) snaps which insert into the phone's female holes. seidio says start at the bottom, 6 o'clock, and then go clockwise to 9, 12 and lastly 3 o'clock. seidio went from one extreme with a loose, crappy cover for the captivate to an overly tight cover which is too hard and inflexible. an overly rigid/tight fitting cover is good and bad. good that it is solid, but bad as it is too difficult to install or remove, frustrating and time consuming. put your phone on a hard surface, not a bed, on top of a paper towel or soft clothto prevent the front gorilla glass from being scratched. my very serious concern is if you take the sgs2 seidio cover off a lot, over time the protruding, hard male snaps will break off because the cover is either too large making it too tight, the snaps are too rigid, or the snaps are too thick. i guess the phrase "watch out what you wish for, because it may come ture" comes to mind. 4. my new seidio extended battery was pre-charged @ 40%. 5. yes, it doubles the weight and thickness, but i am ocd on battery life, so i do not care. if you care, don't get it. for me, i actually like the more meaty feel. 6. will it block nfc when nfc is released? i do not know. end.