Antique look grip style buckle which will fit the 30mm wide straps listed here or can be bought with a strap here.
To fit the buckle lift the catch on the back of the buckle and the strap will slide out and then push the catch down with the strap in and the teeth will grip the leather, see picture.
Choosing your belt size:
All my belts are measured from the fold in leather at the buckle end to the middle of the six buckle holes and not the end tip.
Measure your actual waist and add 2 inches to allow for clothing worn underneath, or the best way, measure your current belt from the fold in leather at the buckle end to the buckle hole you use the most and feel comfortable with.
Please don't use trouser sizes as they can stretch and shrink over time, especially jeans.