G'day Sandy,

No, the Comfort Plus SI Rectangular models are part of their current range. I'm not sure which version of the Sea to Summit website you're looking at, but from what I can see they don't actually list each size of the mat on their own website. The Comfort Plus SI actually comes in 3 different lengths of the tapered mat, and two different sizes of the Rectangular mat.

G'day Tom,

We tend to find that these two mats hit a slightly different market and purpose so while they're comparable, they're a little different. The Comfort Plus SI Rectangle sleep mat is a combination air and foam mattress that will keep you super comfortable, but with a packed size and weight that is probably best suited to trips with a large pack, or where you're not too worried about carrying too much weight. These tend to be purchased mainly by people doing a single overnight walk, kayak trip, motorcycle trip or similar. The Ether Light Sleeping Mat is an air-filled insulated mat that is also super comfy, but packs down much smaller and lighter, and tends to be purchased by multi-day hikers. Overall both mats are going to be on the upper end of comfort with 8cm and 10cm thicknesses. In terms of durability, the Ether Light is 30/40D nylon, which performs well. The COmfort Plus SI has a 30D polyester finish, that is also durable, yet nice and comfortable to sleep on. 

G'day JJ,

Yes they are very similar mats mate, however Sea to Summit have designed the Tapered Sleeping Mat specifically with women in mind.  It offers comfort and support in areas specific to the female body which isn't to say that a male couldn't use it, its just the main difference when comparing to the CP Rectangle Sleep Mat.  Given the slimmer design of the Tapered Mat, it is of course a few grams lighter as well (0.895Kg as against the 1.265Kg on the Rectangle) but apart from these details, the technology and specs stack up the same.  Hope that helps!  Cheers :)