The O2 Mark dildo can be used for both solo and couple play. I bought it because I wanted another realistic dildo which would fit into my RodeoH harness (I feel that my Goodfella is slightly too heavy for it), and also for use on myself, in the form of anal penetration whilst masturbating. This toy is of course also capable of being used for vaginal penetration, but I have zero interest in using it for that.

This dildo is very well suited for anal penetration, due to both its flared base (which is absolutely essential when choosing toys for anal penetration) and its average size. The O2 Mark has an insertable length of 5 1/2 inches and a width of 1 3/8 inches, which makes it large enough to provide a bit of a stretch, but not so big that is painful or unusable for anal penetration.

The flared base on the O2 Mark also means that it fits into strap-on harnesses very well. It is a perfect fit for my RodeoH harness, and it's light enough that it doesn't weigh down the front of the harness too much - the combination of this light weight and the curve in the shaft means that it sits straight in the harness and doesn't sag as much as my Goodfella does.

The O2 Mark is made from Tantus's dual layer O2 silicone, which consists of a firmer inner core and a softer, slightly squishy outer layer. This combination of silicones provides the toy with a more realistic feel than many other dildos, which are often far too firm to properly mimic a real penis. The head of the dildo is also quite soft and squishy, which allows for easy and comfortable insertion.

This is a very realistic-looking dildo, complete with veins along the shaft and even a small hole on the head to mimic a urethral opening. The silicone is very smooth and soft, with a matte texture on the shaft and a more glossy texture on the head. It also has no notable odor, which is great!

I really love the design of this dildo. I only buy realistic looking dildos (so that I will be able to use them in a harness for penetration of a future partner), and I can be quite fussy with what I want them to look like. The highly realistic look of this toy, including details like veins on the shaft, was probably one of the main things about this toy that first caught my eye.

Although a lot of Tantus products are quite similar to the O2 Mark in terms of realistic design, the size of this toy was also a major selling point for me. With 5 1/2 inches of insertable length, the O2 Mark is around the size of an average cis man's penis (or perhaps a little bit bigger, depending on different sources). I am very happy with the size of this dildo, and I think it is suited to both beginner and intermediate users. I wanted an average-sized toy which I would be able to use both on myself and another person, and the O2 Mark fit this requirement as well.

Due to the high degree of realism of this toy, it's obviously not at all discreet.

The highly realistic design of this toy - including both the details on the shaft and head, and the high quality dual layer silicone - is probably the best feature of this dildo. I am finding it very hard to think of a criticism of this toy, apart from the fact that it would be perfect it had balls as well (ideally, ones similar to those on the Goodfella, which are unique because they sit in front of a harness rather than being trapped within it).

The O2 Mark is harness compatible, and fits perfectly into my RodeoH boxer brief harness. It's a very good weight and length for use in this harness, as it's not too heavy as to weigh down the harness and sag downwards. Instead, it sits straight out in front and is easily maneuvered.

Apparently the O2 silicone with which this toy is made often attracts lint, although I have not experienced this personally. However, it is possible for silicone to react badly when it comes into contact with other silicone (apparently it can melt/fuse together), so you will need to keep the O2 Mark away from both silicone lube and other silicone toys. You should only use water-based lubes with this toy.

Cleaning is very simple, you can just wash it with some warm water and soap and it'll be fine. I often use the EdenFantasys toy cleaner wipes that you can get as a free gift with purchases, and they do the job admirably. One method I use to minimize clean-up is to just use a condom on the dildo when I'm using it, and then there's barely any clean-up to worry about after I'm done.