Marmot Precip Full Zip Pants
Marmot Precip Styles
Marmot makes two styles of Precip pants: Full Zip Precips and Regular Precips. The Full Zips are designed for winter hiking, backpacking and climbing. They are sometimes called "New Style" Precips by online retailers because they were introduced after regular Precips (also called "Old Style") which only have calf high boot zips. I own a pair of each.
I recently bought a pair of Marmot Full Zip Precips to replace a pair of Mountain Hardware Cohesion pants that I sliced to ribbons learning to use crampons, and now that I've tried them, I like the Precips better. Both of these pants have full side zips, and I use them as a second windproof shell layer over a compression short or lightweight long underwear.

Winter Layering
Personally, I feel that full length side zips are a must-have requirement for any serious cold weather pant layering system. Sweat buildup in winter should be avoided and side zips provide you with the ability to aggressively vent any moisture buildup in real time. In addition, having side zippers eliminate the need to remove your boots, crampons, snowshoes, or skis before you put on or take off a pants layer. This is good because you don't want to stop moving for very long in winter and get cold.
The side zippers on the Precips work very well, they are much larger and don't jam nearly as often as the tiny zippers on the Cohesion Pants. They are also two way, so you can pull them down from the top and/or up from the bottom. If you want to take off the pant without taking off your boot, simply zip both zippers to the top of the pant, undo a velcro attachment on the waistband and the leg comes right off. Do the same on the second leg and you can take the whole pant off. What would the world be like if all pants were like this?
In addition to the side zips, the Full Zip Precips have one front pocket and two back pockets that close with zippers and are great for carrying small stuff. The pants themselves are made with a breathable multi-layer laminate Gore-Tex knock-off and have fully taped seams to prevent leaks. And finally, they weigh 12.7 oz. in a size XL (mens.)
The only thing I don't like about these pants is that they're a bit baggy around the lower thighs and knees, but I can live with it.
I must confess, it was pure luck that I decided to buy these Precips. Having destroyed one pair of shell pants with crampons already, I didn't want to spend a lot of money to buy another pair of winter pants that will probably meet a similar fate, sooner or later. At $90/pair these are a good deal.
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I’ll be hiking the JMT from July 12 – Aug 4 and need a rain bottom. Should I get the full zips or the calf zips? They will function mainly during downpours, but I can see wearing them to the Mt. Whitney summit for wind protection.
If you’re only going to buy one pair, I’d get the full zips, especially if you’re going to be hiking the JMT with lots of high peaks so you can vent and even remove them without taking off your shoes/boots.