Hola!
REN is one of my favourite skincare brands at the moment: I love the general no fuss ethos, and the fact that all the products give tangiable results. By being a little bit of a savvy shopper I have managed to try quite a few of their products - I bought the kit for combination skin direct from REN, and as my first time buying from them, coupled with a couple of discount codes I picked up, I think the kit cost me around £12:
With this kit I also received a few good sized samples.  Then I noticed the ClearCalm kit on ASOS for £9 and thought "hey, why not!":
Both kits were ridiculously effective, and I have now decided that the ClearCalm range is my fave.  But today we are not talking about generalised skincare, but particularly about REN masks:
Today we are dealing with the ClearCalm 3 Clarity Restoring Mask, Glycolactic Radiance Renewal Mask and the Invisible Pores Detox Mask.  Now, these masks are all pretty raved about in the blogosphere, and to be honest, I can completely see why.  REN have formulated almost an entire wardrobe of masks to deal with any issues you may have, and the best part is that they are extremely effective in their respective skin fields!

As you can see from the photos, each is a very different texture to the next: the ClearCalm 3 Clarity Restoring Mask is a loose clay mask, the Glycolactic Radiance Renewal Mask is a sticky texture, that smells like sweet orange juice, yum, yum, yum, and the Invisible Pores Detox Mask is a very thick clay-like texture.  All have their own particular selling-points, and to be honest, when I'm back working, I shall be buying them all!
First up, the ClearCalm 3 Clarity Restoring Mask.  I feel that this, out of the 3 is the most useful, and multi-purpose mask.  When you squeeze it out and apply, a lovely herbally smell rushes over you, and you instantly feel the calmness that it will bring to your skin.  It is thick in texture, as a clay mask should be, and I love a clay mask as I always feel like they're actually doing something.  This particular mask actually doesn't fully dry, it stays somewhat tacky to the touch, which means rinsing it off it a fairly easy task.  So, why is this such a good mask?  I find that in times of stress, when skin isn't quite behaving, or when a breakout is occuring, this is the mask to use: it soothes, calms, and attacks breakouts all while moisturising the skin a little.  See, perfect multitasker - if you want to try out a REN mask, this should be your first stop.
Next we have the Glycolatic Radiance Renewal Mask.  Now this caught my eye due to the 'glycolactic' of the name: in my days as a Beauty PR I learnt an awful lot about skin resurfacing and AHAs etc etc, and from the name, as I'm sure many of yoou did, I saw that this contained both Glycolic Acid and Lactic Acid.  These are some of my favourite skincare ingredients - chemically exfoliating the skin, and helping to firm and aid the skin in its anti-ageing fight!  Slap a load of this on, then don't touch your sitcky face, wash off, and you now have bright, soft skin!  I like this a lot, it is a less potent version of my Alpha-H Smoothing and Perfecting mask, so is more suitable for more sensitive skins.
Last of all we have the Invisible Pores Detox Mask.  Now this is a thick, thick, thick mask that cleans the skin from the inside out!  You pump out a little of the heavy duty clay, spread it all over and wait.  Wash it off, and you are left with smaller pores, and soft, clearer-looking skin.  I feel that this is the mask I could probably do without, I'm not hugely concerned about my pores, and this is a temporary effect anyways. 
I hope this little foray into the world of REN masks helped you a little, like I said, REN skincare is absolutely lovely, and I tend to come back to it when my skin is playing up as it always delivers results!
Love A.x