a) size: in most cases the size of the gap will be fine (example (piston seal): cylinder diameter, gap diameter and length on the piston). But every additional information can be helpful to avoid problems, like measure several points (is the cylinder or rod still round? the sizes might changed over years of usage, has the cylinder on the beginning, middle and end the same diameter?). Has the former seal any size or brand name printed on it (and did it work well?).
b) Material: Most seals are made of NBR or PU, are the standard material for hydraulic and pneumatic. On "normal" hydraulic/pneumatic devices you will either find black NBR (or NBR fabric) or if any other color it is PU. But as soon as the temperature is high (hot press), very low (example forklift in deepfreeze area) or there is any other media than hydraulic oil, please contact us. Attention: there are some tests (pen size tools) around which claim to be able to determine the material. These devices DO NOT work reliable.
c) Shape: That should be relative easy with our pictures online.
d) If you feel unsure on something please provide us with as many details as possible: working temp., media, sliding speed, length of the cylinder, pressure, condition of the hydraulic system/years of usage. If available technical drawings of the system. What the machine is used for. How many hours per week the machine is used and any former problems with seals.
e) On orders please tell us which shipment you prefer. Usually there is standard priority mail which can be very slow (7-10 days) or FedEx (1-3 days). Smaller orders are usually 4 USD per priority mail or 19 USD for FedEx (what can be fit in the FedEx envelope and is lower than 0.5 kg).