Cobra GT3240VZ grass trimmer review: a budget-friendly cordless design

The Cobra GT3240VZ grass trimmer is a cordless cutter that does exactly what it’s supposed to, without fuss or fanfare. It is part of Cobra’s 40v Li-ion system of lawn mowers and handheld garden tools that can share batteries and charger, which saves money and shed space. I am lucky enough to already own a cordless Cobra lawn mower, which I love, so I saved around £173 by already having a battery and fast charger to hand. 

Our main garden is kept under control by a ride-on (or robot mower if I’m testing one), and the front garden by the aforementioned Cobra lawn mower but none of these garden tools are capable of getting right to the lawn edges, around flower beds or tight up to pathways and steps. 

When our ancient petrol strimmer (that was heavy, smelly and unfathomable to start) died, I was ready for something smaller, lighter and more manageable. When shopping for the best strimmer, I knew I didn’t want any fancy functions that I’d never work out how to use. I just wanted to get our lawns smartened up as quickly and easily as possible. 

Oh, and because a new grass trimmer isn’t nearly as exciting for me as, say, a new handbag or trainers, I was also keenly focused on price. I bought the Cobra GT3240VZ grass trimmer to keep, but this review follows the initial opening and three week’s worth of strimming (once a week after mowing). The initial strim, the first of the season, was naturally much tougher going than the subsequent two. 

Keep scrolling to see how we got on then head to our best strimmer buying guide for more finishing touch options for your lawn.

 Cobra GT3240VZ grass trimmer: product specifications

• Power type: 40v Li-ion battery (not included)
• Battery life: Up to 80 mins
• Charging time: Approx. 90 mins
• Warranty: 2 years
• Cutting width: 28-32cm
• Cutting Line: 1.6mm Twisted Line
• Weight: 4kg

First impressions of the Cobra GT3240VZ grass trimmer 

Upon opening the cardboard box, I found exactly what I was expecting – a fairly basic but well-built grass trimmer. The Cobra GT3240VZ is clearly not aimed at professional/industrial use but nor does it look flimsy or cheap. I was also (and always) pleased to spot that it wasn’t going to require a lot of complicated construction before I could begin blitzing those nettles.   

Setting up and getting started

The instruction manual boasts simple illustrations along with explanatory text, which is better than those I have tried to follow with images or text only. To assemble, I needed to attach the safety guard onto the motor housing with two small screws. Make sure the cutting line isn’t trapped on the wrong side of the motor housing before you screw it down, like I did…oops! 

Attaching the handle and shoulder strap went without a hitch, and then all I needed to do was slide in the battery. I specifically bought a Cobra trimmer because I already had a Cobra 40v battery and charger from my lawn mower that will fit it, but you’ll have to buy one separately if you don’t. You also need to remove the blade cover, which is just there for safe transportation, before you start trimming. 

What is the Cobra GT3240VZ grass trimmer like to use?

To turn the Cobra GT3240VZ grass trimmer on you need to depress the safety lock and the switch trigger simultaneously. It’s a simple action that feels intuitive as part of your overall grip, although I did lose my hand position a couple of times while trimming which just meant I had to turn it back on again. Mildly annoying but no biggie. 

As a novice with a trimmer, it took me a little while to suss the best angle to trim the grass effectively. And without scalping the lawn! But once I’d nailed the angle (about 30 degrees to the grass) and perfected the Cobra-recommended technique of cutting from the top and working down on areas of tall overgrown grass/weeds, it sloughed through the chaos. Not quite like a knife through butter but very close. 

I found the Cobra GT3240VZ grass trimmer surprisingly noisy for a battery-powered garden tool – ear defenders are recommended – but not so loud I couldn’t listen to an Audiobook on my AirPods (under the ear defenders) as I worked. The vibrations were also quite noticeable and in fact my hands were shaking, very slightly, for several hours after I’d finished trimming all around our garden on the first, longest, attempt. The second and third goes, a week apart, were quicker and therefore much better on the hand-shaking front.

Ease of use

At 4kg, the Cobra GT3240VZ isn’t the lightest grass trimmer on the block but nor is it the heaviest. The shoulder strap, when properly used, takes a lot of the weight off the arms, which is very helpful if you’re not built like The Hulk. I found the adjustment kept sliding on the shoulder strap, so I grabbed a trusty safety pin and pinned it firmly down. Again, mildly annoying but easily solved. 

The telescopic height adjustment on the trimmer itself was very simple to adjust and, happily, stayed locked firmly in place. Once I’d mastered the standard trimming swing (back-and-forth, like using a metal detector), it took just over an hour to trim all the garden borders and edging in our approximately 1000sqm garden. There was still a little juice left in the battery had I needed to continue, but barely any in my own tank so I was very glad to be done. 

Using the Cobra GT3240VZ grass trimmer as a neat path edger was a little beyond my skillset. It was easy enough to rotate the trimmer to get the motor head at the right angle via a push-and-turn button near the motor. You can then use the metal plant guard as a guide, which definitely helped but my lines were embarrassingly wonky on the first attempt. Two more goes, and I was showing signs of improvement but wouldn’t win any prizes for precision. 

Admittedly this was probably due to user inexperience, but a supportive edging wheel would have helped carry the weight of the motor, and, I’d like to believe, would have produced neater or at least straighter lines along the paths and lawn edging.   

Additional features

As I’ve mentioned, there are few bells and whistles on this entry-level grass trimmer but, with the exception of the edging guide wheels, I’d say the Cobra GT3240VZ has everything needed to keep your garden trim. 

To lengthen the cutting line, which will inevitably get shorter as you cut, you just have to tap the spool button gently on the ground while the trimmer is turned on and spinning at full bore. There is also a button on the spool casing to allow you to do it manually. Fancier machines will have fully automatic line extension, which means there is no lull in trimming action. 

One feature I did appreciate was the battery power indicator on the 40v battery, which lights up at the touch of a button to show how much power is left. Speaking of power, the battery lasts 80 minutes, which was enough to trim our whole garden and then get the lawn mower out, switch the battery across, and tackle the small patch of lawn at the front that the ride on mower can’t reach.

The cutting line is supplied in cartridge form, which means there’s no annoying and fiddly rewinding of cutting line required. I haven’t needed to replace the line yet, but I did go through the motions for the benefit of this review and can tell you it’s an easy four-step process that’s similar to changing the spool in a sewing machine. If that’s not helpful to you, the instruction book provides good directions. 

There is also a metal plant protection bar, which allows you to trim around delicate plants and shrubs without risk of decapitating limbs. I mainly had it pinned back out of the way as I didn’t feel I got close enough to what needed strimming with it on, and luckily my foliage survived. 

How does the Cobra GT3240VZ grass trimmer compare to other grass trimmers?

I chose the Cobra GT3240VZ grass trimmer primarily because I already own the battery and charger but also because I have been very impressed with the build quality and performance of my Cobra mower. 

For an extra £20 you could get the Cobra GT3024V grass trimmer, which is much lighter (2.4kg) and has a few more features, like an edging guide wheel, adjustable power and slightly more speed. However, battery life is only 30 minutes and, as mentioned, I was looking to spend as little as possible. 

The cheapest Cobra grass trimmer, the Cobra GT600E (£49.99), has a cable, which I suppose would be a good option for anyone who doesn’t already have the battery and charger but does have outdoor power sockets and a relatively small garden. I’d need about 16 extension leads to get it around our garden.

 About this review - and our reviewer

Linda Clayton

Linda is a long-established journalist working in the homes and interiors sector and has tested many products over the past 20+ years, including home tech, appliances, gym equipment, garden tools and mattresses.

She lives in Devon with her husband and their two daughters, in a Victorian property with a half-acre plot. She’s not a skilled gardener but she’s trying very hard to pretend that she is, with a little help from her green-fingered mum! 

She bought the Cobra GT3240VZ grass trimmer and put it through its paces three times for the purposes of this review and is hoping to continue using it for many years to come. She will update this review if its performance changes or issues arise after more extensive use.