How to choose an adapter for a thermal clip-on: measure one number and you are done
You bought a thermal clip-on and there is no adapter in the box. That is not a mistake – the adapter is chosen to fit your riflescope, and this is exactly where most errors happen. This article shows you how to pick the right adapter in five minutes without the risk of receiving the wrong size.
What the adapter is and why you need it
A thermal clip-on mounts in front of the objective of your day scope. To hold firmly and return to the same position every time, you need an adapter ring between the clip-on and the scope. The adapter is fitted to the scope objective once; the clip-on then goes on and off in seconds – with no re-zeroing.
Left to right: thermal clip-on, adapter, scope objective. The adapter clamps onto the objective tube; the clip-on screws or clicks into the adapter.
The only number you need: the objective outer diameter
Adapter size is given in millimetres and means the outer diameter of the scope tube at the objective end. The most common mistake: the number in the scope name is not the adapter size. A 3-12×56 scope has a 56 mm lens, but the tube around it is larger – typically 60 to 64 mm. A Meopta 3-12×56, for example, needs a 62 mm adapter, not 56.
Measure the outer edge of the tube with callipers, not the glass. A ruler or tape is not enough – 1 mm decides whether the adapter fits.
How to measure the diameter in a minute
- Take a pair of callipers (digital or vernier). If you do not have one, borrow one – any locksmith, mechanic or fellow hunter has one.
- Measure the outer diameter of the tube just behind the objective, where the adapter will sit. Measure at two positions 90° apart to rule out error.
- Note the result to a tenth of a millimetre, e.g. 61.8 mm.
- Choose the adapter of that size. If your exact size is not listed, take the next larger one – the adapter tightens down. Never take a smaller one.
No callipers, or not sure? Send us your scope model – in most cases we can look up the diameter and pick the adapter for you.
Which adapter for your clip-on
For HIKMICRO Thunder 2.0 (TE19CR, TQ35CR, TH35PCR), Thunder 3.0 (TH35C, TQ35C, TQ50C, TQ35CL, TQ50CL) and ThermTec Hunt clip-ons we offer two adapters. Both hold zero; they differ in the number of sizes and in design.
| Original HIKMICRO – recommended | Rusan MAR – alternative | |
| Sizes | 30, 40, 42, 44, 50, 56, 58, 62 mm | 33, 41, 42, 50, 53, 56, 57, 58, 60, 62, 63, 63.5, 64, 65, 68 mm |
| Design | one-piece, M52×0.75 thread | two-piece: adapter on the scope + MCR reduction ring on the clip-on, with lock |
| Best for | most scopes, the simplest solution | unusual diameters and hunters who move the clip-on between rifles often |
| Where to buy | Original HIKMICRO adapter | Rusan MAR |
Simple rule: if your diameter is in the original's range, take the original. If not, take the Rusan MAR – 15 sizes cover almost everything.
Pixfra clip-ons (Taurus, Sirius) use their own adapter: Pixfra clip-on adapter, chosen the same way by outer diameter.
Fitting in three steps
- Measure the objective outer diameter with callipers.
- Fit the adapter to the scope objective and tighten the lever. The adapter stays on the scope permanently.
- Attach the clip-on to the adapter – screw or click it in and lock. Done; the clip-on holds your scope's zero.
Frequently asked questions
Do I have to re-zero after fitting the clip-on?
No. The clip-on takes over the day scope's zero. We only recommend a check shot after the first fitting – as with any change to the rifle.
Can I use one clip-on on two rifles?
Yes, as long as each scope has its own adapter. You just move the clip-on. With the Rusan MAR, the MAR adapter stays on each scope and the MCR reduction ring stays on the clip-on.
My scope has a rubber sleeve or sunshade on the objective.
Measure the tube underneath. The adapter clamps onto the metal tube; the rubber usually has to come off.
The adapter fits but the clip-on has slight play.
Check that the adapter is tightened in the right place (not on the tapered part of the tube) and that the clip-on is screwed in fully. If the problem persists, contact us.
I have an older Thunder 1.0 or Cheetah.
These models use a different bayonet system and the Thunder 2.0/3.0 adapters do not fit them. Write to us and we will advise.
Summary
Measure the objective outer diameter with callipers, pick that size from the original HIKMICRO adapter, and if it is not there, go for the Rusan MAR. Not sure? Send us your scope model – we will pick the adapter for you and your clip-on will arrive ready for its first night in the field.