Despite so many of them making the same design mistakes, the male masturbation sleeve has gone through surprisingly little evolution over the last few years. Again and again, companies offer up variations on the same theme - a tube of rubber, jelly, Cyberskin or silicon with a hole at each and and some bumps in the middle.

As far as designs go, it's never been a perfect one. Simple sleeves like that are difficult to get to grips with, tough to even insert yourself into unless you've got a strong erection and the 'hole at both ends' design means that men on the longer side often 'pop' out of the top, which can leave the glans unstimulated when it needs stimulation the most.

Rather disappointingly, the Sinclair select intimate grip makes almost no innovations from this tried and untested design - being basically the same old sleeve design rendered in a swanky clear Cyberskin and featuring a little more girth and length than average.

It's intended to be used the same way as all the other sleeves - insert your erection in one end and stroke the sleeve up and down your shaft. Like with other sleeves, men on the longer side will 'pop out' of one end, while a textured exterior makes it only slightly easier to grip than a regular sleeve.

The Sinclair is made from Phthalates-free Cyberskin, which is a bonus to those of us worried about the affects of BPE and other chemicals. The downside of this is that the Cyberskin is on the firmer side. While some Cyberskin feels literally like skin - with the same softness and give - the Sinclair feels a bit more like silicone - yet without the hygiene benefits.

Firmness is always subjective, but I've always preferred material that's on the softer side. It gives less stimulation and is more like 'the real thing.' The Sinclair was a bit too firm and hard.

If the Sinclair corrects any of the common design oversights of masturbation sleeves, it's in size. Nicely proportioned, the Sinclair can accommodate men of broader girth and length. What's better than that, though, is the size of the 'entrance' hole. One common problem with masturbation sleeves - especially ones on the firm side, like the Sinclair - is that they're difficult to 'insert' yourself into unless you're rock hard. The Sinclair has a slightly larger entrance hole, making it easier to get into.

The textured exterior is also pretty cool - making it easier to grip even with hands that are slippery with lube.

Masturbation sleeves are not exactly high-tech, even if the materials they're made out of are. A simple tube of Cyberskin, the Sinclair has no controls, adjustment or sophistication beyond being able to increase the tightness by gripping it harder.

Cyberskin is a nice material to use, but requires a little care to maintain. You must stick to water-based lube - oil or silicone will destroy it. Also, make sure to dry the product after use to keep the texture nice. Being a simple sleeve of Cyberskin, the Sinclair is ultimately a very easy product to clean - you can just rinse it out under the tap.

One of the other impressive things about the Sinclair is the packaging - coming in a beautiful white box (which is impossible to open without a physics degree) emblazoned with some impressive marketing. While the product itself isn't spectacular, the box certainly wouldn't tip you off to that.