Subhasis has passed on this enquiry to Peter and I.
We may be able to help with the customer's requirement, however, the information provided is too vague.
To be able to assist further I would need to know the following information.
1. What type of core barrel is the core bit being used with ?
2. What is the outside diameter of the core size requirement ?
3. What type of rock is to be drilled ?
Lastly, "Wintech" appears to be a reference to a brand, see below, please confirm.