حلقات O من مطاط بونا-ن نتريل | AS568-439 | داش 439 | صلابة 70 | أسود (20/عبوة)

Had to replace the old seals in a coolant system, and these o-rings held up perfectly under the heat after a full day of operation. The material feels durable and hasn't shown any signs of swelling or cracking.

These fit perfectly on my hydraulic fitting, and the 70 durometer feels firm enough to hold pressure without being hard to install. I've used cheaper o-rings before that cracked in the heat, but these have held up well so far.

Needed a few of these to replace worn-out seals on a hydraulic fitting, and the -40°F to +250°F range gives me confidence they'll hold up in my unheated garage. The 70 durometer feels just right, not too stiff but not flimsy either.