This study examined the linear dimensional stability of nonaqueous elastomeric impressions made from stock and custom trays by measuring casts derived from those impressions at 1 hour, 1 day, and 1 week. There was a small statistical difference among casts produced from stock versus custom trays compared to the master model. However, there was no significant difference in casts produced from impressions poured at 1 hour, 1 day, and 1 week. A custom tray with a 2.0 to 2.5 mm tray spacing had the least amount of variation, yet the differences between custom and stock trays may not be clinically significant.