It is a bit of a jigsaw puzzle working out how to fit the head, there are several different sized washers and it is just a case of trial and error. There are no instructions. See the video for how I fitted it to my Honda strimmer. In all fairness it is not difficult to sort out. The manufacturer states that it will fit almost all makes and models.
This is the second Jet -Fit head I purchased, the first was returned because I wanted to use the thickest Flexiblade (4mm) and the head that I ordered would not take 4mm. So be careful when ordering as there is very little information on the pages as to the size of Flexiblade these heads will accommodate.
I have a large area of scrub to clear, some of it very thick. I have been using the Oregon Brushcutter Blade very successfully, but this is a metal blade and is not very practical for general strimming. It keeps striking rocks and stumps under the scrub and strimming up to walls and fences is difficult, with the Jet-Fit this is not a problem. So now that I have moved on to an area that requires scrub and general strimming activities I need a head with strimmer chord. The Jet-Fit deals with the thick scrub, see the video, but it does tend to wear out the Flexiblade quickly on the very thick stuff. On the video the scrub was just thick and there was not an issue with the Flexiblade chord.
I absolutely love the Jet-Fit it deals with everything with ease. Changing the chord is very quick and easy. It is a joy to use. One thing I did notice is that the description says it is supplied with 3mm and 4mm Flexiblades. I bought a spool of 4mm flexiblade and it is way thicker than the blades supplied. I have been using the spool not the supplied blades. The Flexiblade is very hard and you need to decide whether you want to buy a spool and snip it (which is a little difficult for the 4mm) or buy the pre-cut lengths. I would advise you to get some flexiblades with the head if you decide to get it as it only comes with 2 precut lengths of each diameter.
If you are looking for a good all round strimmer head for a number of different tasks, this is the head for you. I would suggest going for the 4mm flexiblade if you are intending to strim thick brush. I do not think you will be disappointed with this product.