While there isn’t much to a spool a spool can actually be really really good or really really bad. One of the biggest advantages to the halcyon defender spools are that the spool itself doesn't have an open hole. This is a benefit because all too often divers Are told to stick their fingers in the holes and they can get stuck and pull the diver up on an smb deployment. The beveled spool prevents this and increases control being able to hold it tighter or looser. Some spools have an excessively large hole for dry gloves to fit inside but without gloves its awkward to hold. Keep it simple. Some spools are very expensive some are cheap or poorly made. The line, the stainless snap and the spool construction of the Defender safety spools are flawless, making these my go to finger spool always.