Like all Rycote products, these are well designed and manufactured. The plastic used is reassuringly stiff and the inner surface is lined with rubber so they grip microphones securely and resit shifting, even without using the little rubber loops that are intended to pull the clips together to secure them even more firmly.
I have used these with various pencil microphones, including the Sennheiser MKH00 and MKH8000 series microphones, for MS and even double MS, although the latter was slightly precarious though serviceable for a few tests.
Given the quality, the price is reasonable.