Copied the following from the 2016 ACU Handbook:
SECTION 14 GENERAL TECHNICAL SPECIFICATIONS
14.1 PROTECTIVE CLOTHING
During practice and racing riders and passengers must wear the following clothing and footwear:
1. A complete all in one leather suit of at least 1.2mm in thickness on all parts of the suit. Suits
zipped together at the waist are not permitted. Non-leather material may be used if it meets
with the following requirements.
2. The following characteristics of the material must be at least equivalent to 1.5mm of cowhide
(not split leather)
Fire retardant quality – Resistance to abrasion – Coefficient of friction against all types of
asphalt – perspiration absorbing qualities – Medical test – non toxic and non allergenic –
Fabric of a quality that does not melt. It must be non-flammable.
3. The following areas must be padded with at least a double layer of leather or enclosed plastic
foam at least 8mm thick: Shoulders, elbows, both sides of the torso and hip joint, the back of
the torso, knees.
4. Competitors must wear complete undergarments if they use suits which are not lined. Suitable
undergarments may be of the Nomex type, they may also be of silk or simply cotton. Synthetic
materials which may melt and which could harm the riders skin in an accident are not allowed,
neither for the suit nor for the undergarments.
5. Competitors’ footwear must be of leather or an approved material as per 14.1.2 and a minimum
height of 200mm to provide, with the suit, complete protection. No areas of skin to be left
exposed between the leg of the suit and the top of the boot.
6. Competitors must wear leather protective gloves. No areas of skin to be left exposed between
the wrist of the suit and the wrist of the glove.
7. The use of materials in clothing or personal protection which may generate sparks when in
contact with the ground are prohibited.
Seems to be no specific mention of Kevlar now but it used to be that Kevlar suits were not accepted for passengers at Road circuits, e.g. Scarborough, TT, etc. Certainly they have not been accepted at the TT for a few years for passengers but this year they were preventing drivers too from wearing Kevlar suits, usually after they had gone through the initial clothing scrutineering and done a few practice sessions in them without being pulled up

........ask Mike Cookson about his 'happy' time trying to sort it out
![[brick.gif] [brick.gif]](./images/smilies/brick.gif)
, if you can put up with his choice language as he tells you the tale. He had to change to wearing leathers though and was far from comfortable in them
![[azz.gif] [azz.gif]](./images/smilies/azz.gif)
.......didn't seem to slow him down too much though
If in any doubt give the ACU a call and try to get them to give you a definitive answer, they might have decided since Mike asked the question before the TT.