Fits directly over BEEMAN and WEIHRAUCH (HW97/77) Guides! Drop-in, Replacement size OEM Spring maximum power. Size: 810 (20.5mm) x .125w (3.2mm) x 31 coils, closed/ground/polished Nicely fits the HW/Beeman HW97/77 and Clone airgun guides for OEM+ power. (Note: Less coils are required for the HW97 due to the sliding compression chamber. Although, this spring will perform very well in Hw95/85/R11 and others, with slightly less force compared to the Vortek HW95 OEM replacement spring with 33 coils exactacly matching replacement to the HW OEM spring of 33 coils.) Note: May fit other like size airgun guides