That refers to some weaver
bases that have a narrower recoil lug notch. Being that there is no standard for weaver
bases in regards to the lug or notch specifications, company's might vary in these. TheFfastfire base has a wider lug, but still not true picatinny spec at .206''. I have not seen a case where a weaver
base had too thin of a notch, so I believe you should be fine.