DG enhancers are good and well regarded. they are 43mm dia approx (V callipers on rubber never going to be an exact science). and can be stretched and cable tied as Sake San states.
I have a Bisley somewhere if I find I will measure it is softer so will stretch more and will be about the same starting dia I assume.
FTP900 +Sightron S111 10-50 x 55
AA Pro Target in FWB FP70 stock + MTC Mamba lite
Daystate Airwolf + Bushnell Elite 6500
" life is about the memories we hold and not the things that we own"