Choosing what equipment and clothing to take on a Everest Base Camp trek isn't particularly easy. You will be in the mountains for a least two weeks and the temperatures can vary widely. It can be swelteringly hot, it might snow, rain is likely, you are limited by weight and you won't be able to wash any of it very easily. It's best to pick outdoor clothing that is quick drying, versatile and will combine and layer with other clothing when it gets colder at higher altitudes. In early 2012 I walked the classic Everest base camp trek and stayed a week at base camp hosted by Jagged Globe. I photographed all the key characters involved in climbing Mount Everest, porters, cooks, Sherpas, Kenton Cool, Conrad Anker and Adele Pennington amongst others. The photographs can be viewed here - Everest Base Camp Portraits and the clothing I used is listed below.
Rab Aeon Tee
These base layer tops are brilliant, soft and silky to wear, great on their own when its hot, great layered under other clothing when it's cold, good to wear inside a sleeping bag and they don't smell too badly if you don't wash them much (however they do dry very quickly when you do end up washing them). I have used these in Borneo Jungles, Ice climbing in Norway, for Scottish winter mountaineering, in American deserts and summiting Kilimanjaro. I don't go anywhere without one.
Rab MeCo 165 Long Sleeve Zip tee
Merino wool has been popular as a base layer for a few years now and this Rab long sleeve top is a modern update. 65% merino wool combined with 35% recycled polyester with Cocona® which is derived from discarded coconut shells in a process I don't really understand. However it does work and the great thing about these tops is that they can be used as both a base layer and mid layer over a Aeon Tee depending upon the conditions.
Rab Treklite Trousers
I decided that I was only going to take one pair of trousers up to base camp so I had to be quite choosy. After years of trying various fabrics I have concluded that for hiking pants, a thin stretchy soft shell fabric works best in a variety of conditions. They are very breathable, dry extremely quickly and layer well with thermal underwear when things start to get colder. Choose a dark colour to mask the dirt and dust.
Rab Xenon Jacket
I have been using Primaloft jackets instead of fleece and soft shell jackets as a mid layer for a few years now. They are lighter, warmer, more wind proof, dry quicker and layer better. Again this jacket has been with me everywhere over the last couple of years. Put it on over or under the Rab Infinity when it gets really cold.
Rab Infinity Down Jacket
As you get higher it's gonna get colder and a good quality down jacket will help make those chilly evenings a lot more bearable. I chose the Infinity for its incredible light weight but there are many alternatives including the Rab Neutrino or Rab Summit jacket and if you really feel the cold pick the new Rab Jannu jacket.
Rab Stretch Neo Jacket and Pants
Unfortunately it can rain quite a lot in the Khumbu region of Nepal so a good quality set of hard shell waterproofs is essential. The Stretch Neo jacket and pants aren't the lightest waterproof available but the Neo shell waterproof fabric is excellent. Durable, more breathable than Gore-tex and stretchy.
Rab Expedition 1000 Sleeping Bag
Choosing a sleeping bag is always difficult. Make the wrong decision and those cold, cold mountain nights really drag. Ideally you will need a four season sleeping bag, preferably down which is warmer for the weight and packs smaller. You may find a four season bag a tad too warm lower down but I would rather be too warm early on than too cold higher up. The Rab Expedition sleeping bags are built on the roomy side to accommodate the wearing of high altitude down clothing inside the bag, you won't actually be climbing to Everest summit, so you won't need to do this, but this design does make the bag a bit easier to move around in and the extra internal space may suit larger trekkers. A disadvantage of this extra room is that the bag does take a little longer to warm up. A good alternate would be a Rab Andes 1000.